en/subtitles/17. Core Motion and Camera.srt

﻿1
00:00:00,401 --> 00:00:04,603
[MUSIC]                         

2
00:00:04,671 --> 00:00:07,906
Stanford University.            
>> Well,                        

3
00:00:07,975 --> 00:00:12,477
welcome to lecture number       
17 of Stanford CS193P,          

4
00:00:12,546 --> 00:00:16,815
this is a fall of 2017. Today   
we're gonna talk about some     

5
00:00:16,883 --> 00:00:20,085
hardware specific APIs,         
specifically Core Motion,       

6
00:00:20,153 --> 00:00:23,555
which is the position of the    
device in space, basically,     

7
00:00:23,623 --> 00:00:26,391
as it moves around.             
And then the camera, so         

8
00:00:26,460 --> 00:00:31,496
we can capture images with      
the camera. Now Core Motion     

9
00:00:31,565 --> 00:00:34,233
is really a whole set of        
APIs that go together.          

10
00:00:34,301 --> 00:00:37,569
The primary inputs to Core      
Motion are the accelerometer,   

11
00:00:37,638 --> 00:00:40,505
almost all devices have         
an accelerometer. The gyro,     

12
00:00:40,574 --> 00:00:44,142
most newer devices have         
a gyro. And the magnetometer,   

13
00:00:44,210 --> 00:00:47,846
kind of similar to the gyro,    
newer devices have all that.    

14
00:00:47,915 --> 00:00:50,515
And you're gonna see a part     
of the API we're really gonna   

15
00:00:50,584 --> 00:00:53,017
wanna check and make sure       
that the device we're on has    

16
00:00:53,086 --> 00:00:56,988
the hardware we want before we  
do it. Now the primary API to   

17
00:00:57,057 --> 00:00:59,992
get at all this is this class   
called CMMotionManager.         

18
00:01:00,060 --> 00:01:01,460
There's some other classes      
we're gonna talk about,         

19
00:01:01,528 --> 00:01:04,796
but this is the primary one.    
Now, you can create multiple    

20
00:01:04,865 --> 00:01:07,131
instances of this thing,        
but in a sense,                 

21
00:01:07,200 --> 00:01:09,834
there's only set of hardware.   
So usually in your app,         

22
00:01:09,903 --> 00:01:13,805
you're gonna have one           
shared CMMotionManager to       

23
00:01:13,874 --> 00:01:16,574
collect all the information     
from these devices.             

24
00:01:16,643 --> 00:01:19,511
Now, the way the API works,     
basically, is first you're      

25
00:01:19,580 --> 00:01:21,680
gonna check to see what         
hardware is available,          

26
00:01:21,749 --> 00:01:23,515
all right,                      
that's a very important check.  

27
00:01:23,584 --> 00:01:26,618
Then you can either start       
sampling, okay, just            

28
00:01:26,687 --> 00:01:29,754
asking the CMMotionManager      
what's the current state of     

29
00:01:29,823 --> 00:01:31,857
the accelerometer? What's       
the current state of gyro?      

30
00:01:31,925 --> 00:01:34,593
What's the current state        
of magnetometer? Or             

31
00:01:34,661 --> 00:01:38,863
you can register a closure,     
and a certain refresh rate,     

32
00:01:38,932 --> 00:01:41,566
and it will execute your        
closure at that refresh rate,   

33
00:01:41,635 --> 00:01:44,703
as best it can anyway, and      
tell you what the state is.     

34
00:01:44,772 --> 00:01:47,505
So it's kind of like you can    
either pull the data out        

35
00:01:47,574 --> 00:01:50,341
of it, or it can push the data  
to you. Really either           

36
00:01:50,410 --> 00:01:52,977
model, and it kinda depends on  
how your app works as to which  

37
00:01:53,046 --> 00:01:55,980
of those is appropriate. So     
I'm gonna talk about the API's  

38
00:01:56,049 --> 00:01:58,350
for both of those things.       
So let's do number one here,    

39
00:01:58,419 --> 00:02:00,218
which checking the              
availability of the sensors.    

40
00:02:00,287 --> 00:02:02,720
Really, where you're            
simply are just gonna get       

41
00:02:02,789 --> 00:02:05,824
your CMMotionManager and then   
you gonna ask questions like,   

42
00:02:05,893 --> 00:02:08,360
accelerometer available,        
is gyro available,              

43
00:02:08,428 --> 00:02:11,095
magnetometer available? And     
this is gonna return yes or     

44
00:02:11,164 --> 00:02:12,931
no whether these                
things are available.           

45
00:02:13,000 --> 00:02:16,001
Notice that there's something   
there called device motion,     

46
00:02:16,070 --> 00:02:18,570
you see accelerometer,          
gyro, magnetometer, and         

47
00:02:18,638 --> 00:02:21,272
deviceMotion. So we're gonna    
talk all about deviceMotion.    

48
00:02:21,341 --> 00:02:25,009
It's essentially a combination  
of all the other devices, and   

49
00:02:25,078 --> 00:02:27,912
it allows us to get much        
more accurate readings,         

50
00:02:27,981 --> 00:02:31,716
more interesting readings, by   
combining the accelerometer,    

51
00:02:31,785 --> 00:02:35,253
gyro, and magnetometer. So the  
way where you're going to pull  

52
00:02:35,322 --> 00:02:38,256
the information, okay, not      
gonna register a closure but    

53
00:02:38,325 --> 00:02:40,425
you're just gonna ask for       
as you need it.                 

54
00:02:40,494 --> 00:02:43,594
You do that by calling start    
accelerometer updates, or       

55
00:02:43,663 --> 00:02:46,832
start gyro updates and that's   
gonna tell the hardware,        

56
00:02:46,900 --> 00:02:49,567
tell iOS, hey,                  
l wanna get this information.   

57
00:02:49,636 --> 00:02:52,804
So, if that particular piece    
of hardware has to be powered   

58
00:02:52,873 --> 00:02:55,773
up or something like that,      
then iOS is gonna do that so    

59
00:02:55,842 --> 00:02:58,076
that you can start              
asking the value of it.         

60
00:02:58,145 --> 00:03:02,380
So that's all you have to do    
to start pulling the data.      

61
00:03:02,449 --> 00:03:05,250
You can also find out if        
the hardware is on and          

62
00:03:05,318 --> 00:03:07,919
collecting data with            
accelerometer active or         

63
00:03:07,988 --> 00:03:12,290
gyro active VAR in              
the CMMotionManager.            

64
00:03:12,358 --> 00:03:14,860
Now a really important thing    
to do when you're accessing     

65
00:03:14,928 --> 00:03:18,530
this data from these hardware   
devices is to turn it off,      

66
00:03:18,599 --> 00:03:20,898
okay? The reason you            
wanna turn it off is,           

67
00:03:20,967 --> 00:03:22,567
it requires battery, okay?      

68
00:03:22,636 --> 00:03:26,104
Who knows how much, it depends  
on the piece of hardware, to    

69
00:03:26,173 --> 00:03:28,473
do this, and you don't wanna    
waste the user's battery.       

70
00:03:28,542 --> 00:03:31,109
All right, so we definitely     
wanna turn if off anytime       

71
00:03:31,178 --> 00:03:33,244
we're not using it. Not like    
just when our app quits or      

72
00:03:33,313 --> 00:03:35,813
something, but actually any     
time we are not actually gonna  

73
00:03:35,882 --> 00:03:38,383
use the information, let's      
turn that thing off, right,     

74
00:03:38,451 --> 00:03:41,052
save some battery. All right,   
so now let's talk a little      

75
00:03:41,121 --> 00:03:43,621
bit about that pull interface   
where you're just gonna         

76
00:03:43,690 --> 00:03:46,091
ask for the current state       
of this thing all the time.     

77
00:03:46,160 --> 00:03:47,893
And the API is                  
very similar for                

78
00:03:47,962 --> 00:03:50,729
all the devices, gyro,          
accelerometer, and              

79
00:03:50,797 --> 00:03:55,333
magnetometer, and for this      
combined device motion thing.   

80
00:03:55,401 --> 00:03:56,334
So, here's what                 
it looks like for               

81
00:03:56,402 --> 00:03:58,971
accelerometer, it's just a VAR  
in CMMotionManager called       

82
00:03:59,039 --> 00:04:01,272
accelerometer data.             
Gives you back a struct,        

83
00:04:01,341 --> 00:04:02,974
it looks like this, x, y, and   

84
00:04:03,043 --> 00:04:07,779
z. That is the acceleration     
of the device in x, y, and z.   

85
00:04:07,848 --> 00:04:11,382
So x is the axis that goes      
across the device, okay, so     

86
00:04:11,451 --> 00:04:15,019
if you're looking at the        
device and the home button at   

87
00:04:15,088 --> 00:04:18,556
the bottom and you're looking   
at it. Then across is x,        

88
00:04:18,625 --> 00:04:21,492
y is up and down through        
the home button essentially,    

89
00:04:21,561 --> 00:04:22,995
or you have an iPhone 10,       

90
00:04:23,063 --> 00:04:25,863
through where the home          
button used to be. And          

91
00:04:25,932 --> 00:04:28,666
then z is down through          
back of the device device.      

92
00:04:28,735 --> 00:04:31,636
Okay, so if you had a device    
sitting on a table flat,        

93
00:04:31,705 --> 00:04:34,672
then z would be 1.0 here,       
because this is in g, and       

94
00:04:34,741 --> 00:04:38,142
the only acceleration that the  
device would be experiencing    

95
00:04:38,211 --> 00:04:40,678
is the acceleration             
due to gravity, okay?           

96
00:04:40,747 --> 00:04:42,347
Don't forget about              
that acceleration,              

97
00:04:42,416 --> 00:04:44,849
right, 9.8 meters per second    
squared towards the center of   

98
00:04:44,918 --> 00:04:47,052
the earth,                      
that's always happening. So     

99
00:04:47,120 --> 00:04:49,754
if you then pick the device     
up and kinda set it down so     

100
00:04:49,823 --> 00:04:52,323
that the home button is on      
the bottom, right, then your    

101
00:04:52,392 --> 00:04:56,494
y would be experiencing 1 g,    
and z and x would be 0,         

102
00:04:56,563 --> 00:04:58,229
okay, cuz nothing would         
be moving it. Now,              

103
00:04:58,298 --> 00:05:00,999
if you took the device and you  
shake it all around like this,  

104
00:05:01,068 --> 00:05:03,502
then x, y, and z are gonna be   
all kinds of random numbers.    

105
00:05:03,570 --> 00:05:06,171
Could be much greater than      
1 if you really jerk it,        

106
00:05:06,240 --> 00:05:09,274
much faster acceleration and    
the acceleration due to         

107
00:05:09,342 --> 00:05:11,176
gravity, you could get          
all kinds of numbers.           

108
00:05:11,244 --> 00:05:13,945
All right, so this'll give      
me the raw acceleration         

109
00:05:14,014 --> 00:05:16,014
of the device in space,         
including gravity.              

110
00:05:17,284 --> 00:05:20,418
All right, the gyro,            
so the gyro, we're              

111
00:05:20,487 --> 00:05:23,221
almost never gonna ask for the  
gyro information directly like  

112
00:05:23,290 --> 00:05:25,891
this as you're gonna see in     
a motion. But if you did, it's  

113
00:05:25,959 --> 00:05:28,559
essentially gonna tell you      
the rotation rate around those  

114
00:05:28,628 --> 00:05:32,430
three axes I talk about in      
radians per second. Okay, so    

115
00:05:32,499 --> 00:05:35,834
it's basically how fast it's    
rotating in these devices.      

116
00:05:35,902 --> 00:05:38,937
Now the problem is,             
is the gyro on its own can get  

117
00:05:39,006 --> 00:05:42,374
bias introduced to it. It can   
kind of drift a little bit,     

118
00:05:42,443 --> 00:05:45,243
so the gyro works a lot         
better in concert with          

119
00:05:45,311 --> 00:05:47,946
the accelerometer,              
as you'll see in a moment,      

120
00:05:48,015 --> 00:05:50,582
and similarly with              
magnetometer. Yeah, you can     

121
00:05:50,651 --> 00:05:54,252
find out the magnetic field     
around you but, you'd like to   

122
00:05:54,321 --> 00:05:56,988
know what, how much of that     
is earth's magnetic field,      

123
00:05:57,057 --> 00:05:59,524
so you can find out where the   
north is, versus how much is    

124
00:05:59,593 --> 00:06:02,393
just local interference         
from devices. And so,           

125
00:06:02,462 --> 00:06:05,330
we don't usually access the     
magnetometer directly either.   

126
00:06:05,399 --> 00:06:09,333
Instead, in both cases,         
we access this pseudo device    

127
00:06:09,402 --> 00:06:12,804
called deviceMotion. Okay, and  
so, it's similar to the other   

128
00:06:12,873 --> 00:06:15,173
ones, it has var, this one's    
called deviceMotion, and        

129
00:06:15,242 --> 00:06:18,176
it gives you back this          
deviceMotion struct. Now,       

130
00:06:18,245 --> 00:06:19,877
the deviceMotion                
struct is giving you            

131
00:06:19,946 --> 00:06:21,145
a lot of the same               
information that you're         

132
00:06:21,214 --> 00:06:23,214
getting from these              
other devices, but              

133
00:06:23,283 --> 00:06:26,885
it's combining the devices to   
give you better information.    

134
00:06:26,953 --> 00:06:29,354
For example, let's look         
at acceleration. So,            

135
00:06:29,422 --> 00:06:31,222
when you have a device and      
you're looking at               

136
00:06:31,290 --> 00:06:34,192
the accelerometer, you don't    
really know how much of that    

137
00:06:34,261 --> 00:06:36,194
is due to the acceleration      
due to gravity, and             

138
00:06:36,262 --> 00:06:38,963
how much is because the user    
is moving the device around.    

139
00:06:39,032 --> 00:06:42,700
Right, well, but if you have    
the gyro, now you do know       

140
00:06:42,769 --> 00:06:45,837
how much the user is moving     
the device around, okay.        

141
00:06:45,906 --> 00:06:48,306
So, if you combine the two,     
you can factor                  

142
00:06:48,375 --> 00:06:50,108
out the acceleration            
that's due to gravity and       

143
00:06:50,177 --> 00:06:53,678
the acceleration that's the     
actual user moving the device.  

144
00:06:53,747 --> 00:06:56,314
So in CMMotion,                 
you have the gravity which      

145
00:06:56,383 --> 00:06:59,251
is a CM acceleration, and you   
also have user acceleration,    

146
00:06:59,319 --> 00:07:01,319
and they're separated out.      
Okay, so                        

147
00:07:01,388 --> 00:07:03,955
you see how it's used the gyro  
to give you more information    

148
00:07:04,024 --> 00:07:07,425
about acceleration, and         
similarly for the gyro, okay?   

149
00:07:07,494 --> 00:07:10,594
If you have this gyro, you can  
remove the bias that happens    

150
00:07:10,663 --> 00:07:13,298
with the gyro because you have  
the accelerometer information   

151
00:07:13,367 --> 00:07:16,034
that tells you where            
this thing is being             

152
00:07:16,103 --> 00:07:19,971
moved around as it's being      
rotated. So, there you can      

153
00:07:20,039 --> 00:07:22,807
get rotation rate in the same   
way as you got before, but      

154
00:07:22,876 --> 00:07:25,276
you can also get much more      
interesting in things like      

155
00:07:25,345 --> 00:07:27,912
roll, pitch, and yaw, okay?     
So if you know anything about   

156
00:07:27,981 --> 00:07:31,315
flying, if you have an          
airplane that's flying along,   

157
00:07:31,384 --> 00:07:35,586
the roll is when the airplane   
tilts it's wings side to side,  

158
00:07:35,655 --> 00:07:38,289
right, that's the roll. Pitch   
is when the pitches is nose     

159
00:07:38,357 --> 00:07:41,292
up or down, right, that's       
the pitch. And the yaw is when  

160
00:07:41,361 --> 00:07:44,929
it kinda turns into the wind    
in the same plane parallel      

161
00:07:44,998 --> 00:07:48,466
to the ground, right. So you    
can get that same roll, pitch,  

162
00:07:48,535 --> 00:07:52,036
and yaw in your device, which   
is really kind of a cool way    

163
00:07:52,105 --> 00:07:53,938
to think about your devices,    

164
00:07:54,007 --> 00:07:57,876
what your device is doing. You  
can also get heading, okay,     

165
00:07:57,944 --> 00:08:00,712
now it needs the magnetometer   
for that, obviously,            

166
00:08:00,781 --> 00:08:02,780
to do the heading. And this is  
gonna give you the heading.     

167
00:08:02,849 --> 00:08:04,548
And heading is sometimes        
interesting to                  

168
00:08:04,617 --> 00:08:09,220
have if you have, for example,  
an, augmented reality app, or   

169
00:08:09,289 --> 00:08:12,223
something like that, where you  
wanna know the gyro position    

170
00:08:12,291 --> 00:08:13,591
as you're moving                
this thing around.              

171
00:08:13,660 --> 00:08:15,126
But you also know where         
you are in the world.           

172
00:08:15,194 --> 00:08:18,730
Are you facing north?           
Where are you facing?           

173
00:08:18,799 --> 00:08:20,431
So, we can give you that        
information, as well.           

174
00:08:20,500 --> 00:08:24,235
So, CMDeviceMotion is probably  
the primary way we get          

175
00:08:24,303 --> 00:08:27,472
information out of core         
motion, when we want gyro,      

176
00:08:27,541 --> 00:08:29,374
accelerometer, magnetometer,    

177
00:08:29,442 --> 00:08:32,743
because it combines them        
very intelligently.             

178
00:08:32,812 --> 00:08:35,813
Okay, now when you're getting   
device motion you can actually  

179
00:08:35,882 --> 00:08:40,251
control, which of the devices,  
accelerometer, gyro and         

180
00:08:40,320 --> 00:08:43,154
magnetometer are used,          
specifically the magnetometer,  

181
00:08:43,222 --> 00:08:46,157
okay? There's a couple of       
reference frames and reference  

182
00:08:46,226 --> 00:08:49,627
frame is just an argument when  
you start getting the updates,  

183
00:08:49,695 --> 00:08:53,030
from the device motion. So,     
there's two reference frames    

184
00:08:53,099 --> 00:08:56,467
called xArbitraryZVertical and  
xArbitraryCorrected ZVertical   

185
00:08:56,536 --> 00:08:58,770
which either don't use          
the magnetometer, or            

186
00:08:58,839 --> 00:09:01,339
can work without the,           
magnetometer,                   

187
00:09:01,408 --> 00:09:04,108
I believe they can do.          
And so, they're not,            

188
00:09:04,177 --> 00:09:06,744
they're really not used for     
a reference frame when,         

189
00:09:06,813 --> 00:09:09,413
when you wanna know where       
your device is in the world,    

190
00:09:09,482 --> 00:09:13,852
okay? So, there's two other     
ones. xMagnetic/TrueNorth and   

191
00:09:13,920 --> 00:09:17,622
xMagneticTrue NorthZVertical.   
And                             

192
00:09:17,691 --> 00:09:20,124
those use the magnetometer.     
Now, those actually will        

193
00:09:20,193 --> 00:09:22,560
require the magnetometer        
to be calibrated,               

194
00:09:22,629 --> 00:09:25,329
and, and ready to use, so,      
you know, you don't wanna       

195
00:09:25,398 --> 00:09:28,032
use these reference frames      
lightly, but if you need to     

196
00:09:28,101 --> 00:09:30,902
know where you are then you     
need this. Obviously, for       

197
00:09:30,970 --> 00:09:33,371
true north it not only needs    
to know all the information     

198
00:09:33,440 --> 00:09:35,940
that we talked about so far,    
but it also needs to know your  

199
00:09:36,009 --> 00:09:37,775
location, where you             
are on the planet.              

200
00:09:37,844 --> 00:09:40,077
So, it can tell the difference  
between magnetic north,         

201
00:09:40,146 --> 00:09:42,647
which is the only thing it can  
measure, and true north, okay?  

202
00:09:42,715 --> 00:09:46,184
And that just depends where     
you are on Earth. Now,          

203
00:09:46,252 --> 00:09:48,686
if you want the heading         
VAR that I talked about on      

204
00:09:48,754 --> 00:09:51,556
the last device motion you'll   
need to have the reference      

205
00:09:51,624 --> 00:09:56,260
either be magnetic, or          
true north. All right? Now,     

206
00:09:56,329 --> 00:09:58,963
always check to make sure that  
whatever reference frame you    

207
00:09:59,031 --> 00:10:01,265
want to use, especially if      
it's going to be the magnetic,  

208
00:10:01,334 --> 00:10:03,802
or true north ones is           
available. And you can do that  

209
00:10:03,870 --> 00:10:07,605
with the availableAttitude      
ReferenceFrames, function and   

210
00:10:07,674 --> 00:10:11,542
it'll return one of these       
frames above, and you can       

211
00:10:11,611 --> 00:10:13,344
kinda, it's a bit masked and    
you can look in there and       

212
00:10:13,413 --> 00:10:16,881
see if yours is available.      
All right, so                   

213
00:10:16,949 --> 00:10:19,584
we talked about how to just     
grab the information whether    

214
00:10:19,653 --> 00:10:20,618
it's accelerometer data, or     

215
00:10:20,686 --> 00:10:23,588
this device motion data, grab   
it from CM motion manager.      

216
00:10:23,656 --> 00:10:25,690
And how about the thing         
of registering a closure.       

217
00:10:25,759 --> 00:10:28,859
So, that API looks like this.   
For accelerometer,              

218
00:10:28,928 --> 00:10:30,161
for example you're gonna say,   

219
00:10:30,229 --> 00:10:31,796
startAccelerometer              
UpdatesToQueue,                 

220
00:10:31,865 --> 00:10:34,065
that's the queue that your      
closure is gonna be executed    

221
00:10:34,134 --> 00:10:36,200
on. That's almost always gonna  
be the main queue, so you're    

222
00:10:36,269 --> 00:10:39,603
gonna say .main there usually.  
With a handler, and a handler   

223
00:10:39,672 --> 00:10:41,572
is just a look closure.         
It takes two arguments,         

224
00:10:41,641 --> 00:10:44,509
one is the accelerometer data   
that it's giving you in its     

225
00:10:44,578 --> 00:10:46,877
updates, and the other          
one is a possible error.        

226
00:10:46,946 --> 00:10:49,647
And one of these is always      
nill, okay? Either it,          

227
00:10:49,716 --> 00:10:53,250
it got the data, or it didn't.  
It's as simple as that, okay?   

228
00:10:53,319 --> 00:10:55,119
So, you're just gonna get       
called this closure is gonna    

229
00:10:55,188 --> 00:10:59,757
get called repeatedly with the  
state of the accelerometer.     

230
00:10:59,825 --> 00:11:03,194
Similar for the gyro, similar   
for the magnetometer, and       

231
00:11:03,263 --> 00:11:05,897
similar for device motion,      
okay? Notice, that device       

232
00:11:05,966 --> 00:11:07,832
motion also has this extra      
argument at the beginning,      

233
00:11:07,900 --> 00:11:11,469
which is that reference frame   
I talked about, okay? Now,      

234
00:11:11,538 --> 00:11:14,138
what about the errors that      
can come back here, okay?       

235
00:11:14,207 --> 00:11:16,707
Well, a lot depends on what     
your asking for, especially in  

236
00:11:16,776 --> 00:11:20,078
device motion world. If you're  
asking for something like true  

237
00:11:20,146 --> 00:11:22,580
north reference frame, you're   
trying to get the heading,      

238
00:11:22,648 --> 00:11:25,049
you might get the error True    
North Not Available. Maybe,     

239
00:11:25,118 --> 00:11:27,251
because it doesn't know where   
you are on the Earth, okay?     

240
00:11:27,320 --> 00:11:30,922
Because it can't see any cell   
sites, or Wi-Fi, uh,GPS, or     

241
00:11:30,990 --> 00:11:32,323
anything like that, so          

242
00:11:32,392 --> 00:11:36,460
it doesn't where you are. Also  
you can get NotAuthorized and   

243
00:11:36,529 --> 00:11:38,463
NotAvailable, and we're gonna   
talk about that in a second.    

244
00:11:38,531 --> 00:11:41,432
Where, the user might have      
said, I don't want this app to  

245
00:11:41,501 --> 00:11:43,534
be able to get this             
information from me, okay?      

246
00:11:43,603 --> 00:11:46,103
That's from a privacy           
standpoint. Okay, so            

247
00:11:46,172 --> 00:11:47,572
you want to look in             
the documentation and           

248
00:11:47,641 --> 00:11:49,240
see what the errors you can     
get are and handle them.        

249
00:11:49,309 --> 00:11:52,410
I, core motion same thing       
with the core location and      

250
00:11:52,479 --> 00:11:53,511
the map kit it's a place where  

251
00:11:53,580 --> 00:11:54,712
you really want to              
handle the errors.              

252
00:11:54,781 --> 00:11:56,680
You don't want to               
blindly ignore errors,          

253
00:11:56,749 --> 00:11:58,415
because these errors            
do come up. Okay?               

254
00:11:58,484 --> 00:12:02,687
We're talking about physical    
devices here. Real world,       

255
00:12:02,755 --> 00:12:07,391
it's variable, okay? So, how    
often does your closure get     

256
00:12:07,460 --> 00:12:10,127
called? Well, you get to        
determine that by setting one   

257
00:12:10,196 --> 00:12:12,430
of these vars, the              
accelerometer UpdateInterval,   

258
00:12:12,499 --> 00:12:14,399
or the deviceMotion             
UpdateInterval.                 

259
00:12:14,467 --> 00:12:17,435
This is a TimeInterval, so      
that's number of seconds. And   

260
00:12:17,503 --> 00:12:20,338
usually you're gonna set it     
to maybe a 10th of a second,    

261
00:12:20,407 --> 00:12:24,241
or 30th of a second. Maybe you  
could do 60th of a session,     

262
00:12:24,310 --> 00:12:26,444
but you're really               
pushing it by then.             

263
00:12:26,513 --> 00:12:28,546
And remember, that it's gonna   
be calling your closure, so     

264
00:12:28,615 --> 00:12:30,181
unless your closure's           
really lightweight,             

265
00:12:30,250 --> 00:12:32,117
you don't wanna call            
it too much. So,                

266
00:12:32,185 --> 00:12:34,018
how do you decide what          
to set this to? Well,           

267
00:12:34,086 --> 00:12:36,988
it totally depends on what's    
happening in your app, okay?    

268
00:12:37,056 --> 00:12:38,722
You're gonna see the demo       
I'm gonna do day,               

269
00:12:38,791 --> 00:12:40,525
today I'm gonna use             
the accelerometer.              

270
00:12:40,593 --> 00:12:43,827
Eh, it's not that important     
to see really quick changes     

271
00:12:43,896 --> 00:12:47,165
in the accelerometer, so        
I'm gonna go fairly low rate.   

272
00:12:47,234 --> 00:12:49,967
But I might have something      
that's very detailed            

273
00:12:50,036 --> 00:12:51,669
thing where I'm looking         
at accelerometer, and           

274
00:12:51,738 --> 00:12:53,103
I wanna know exactly            
what's happening and            

275
00:12:53,172 --> 00:12:53,837
the users using it,             

276
00:12:53,906 --> 00:12:55,906
moving it tiny little amounts.  
Then I might want to be         

277
00:12:55,975 --> 00:13:00,545
updating very quickly, okay?    
So there is a limit of course.  

278
00:13:00,613 --> 00:13:02,346
The hardware can only           
deliver certain limit,          

279
00:13:02,415 --> 00:13:05,282
I'm not sure what those limits  
are. Probably around a 60th of  

280
00:13:05,351 --> 00:13:08,820
a second kind of thing but      
that's something you have to    

281
00:13:08,888 --> 00:13:12,323
tune to make your app work      
well. It is okay, by the way,   

282
00:13:12,392 --> 00:13:15,126
to register multiple closures,  
okay, inside your app.          

283
00:13:15,194 --> 00:13:16,927
Have two different things,      
although they're all going to   

284
00:13:16,996 --> 00:13:19,363
want to be updating at          
the same rate, okay?            

285
00:13:19,432 --> 00:13:21,833
And if they're all registered   
with the same motion manager,   

286
00:13:21,901 --> 00:13:23,401
they will all be updating       
at the same rate.               

287
00:13:23,469 --> 00:13:26,370
Okay, it's not really           
recommended to have two core    

288
00:13:26,439 --> 00:13:28,406
motion managers with            
different rates and             

289
00:13:28,475 --> 00:13:31,008
different closures. Cuz you     
could get a performance issue   

290
00:13:31,077 --> 00:13:33,677
there when it's trying to       
service both of those rates     

291
00:13:33,746 --> 00:13:35,946
and it's having to call them a  
lot, so be careful with that.   

292
00:13:36,015 --> 00:13:40,484
All right, so                   
we understand then              

293
00:13:40,553 --> 00:13:44,021
how to get the accelerometer    
data, the instantaneous value   

294
00:13:44,090 --> 00:13:46,790
of the accelerometer.           
But really accelerometer data   

295
00:13:46,859 --> 00:13:50,661
sometimes make a lot more       
sense over time, okay? Like,    

296
00:13:50,729 --> 00:13:53,164
what's the average amount of    
movement in the last minute?    

297
00:13:53,233 --> 00:13:53,865
Or something like that.         

298
00:13:53,933 --> 00:13:55,967
Maybe you're trying to see      
what the user is up to.         

299
00:13:56,036 --> 00:13:59,170
What they're doing. Kinda       
how they're moving around,      

300
00:13:59,238 --> 00:14:00,838
or they're walking around or    
what,                           

301
00:14:00,907 --> 00:14:03,040
they're doing. So, this is      
another class is slow motion    

302
00:14:03,109 --> 00:14:06,844
called CMSensorRecorder.        
And it can record at 50 hertz.  

303
00:14:06,913 --> 00:14:09,313
What's going on now.            
Only newer devices.             

304
00:14:09,382 --> 00:14:11,549
I think iPhone 7 and            
later can do this.              

305
00:14:11,617 --> 00:14:13,984
So, you definitely want to say  
is accelerometer recording      

306
00:14:14,053 --> 00:14:16,020
available? This is also         
something on the Apple Watch,   

307
00:14:16,088 --> 00:14:19,189
which is very useful for that.  
Then once you do it,            

308
00:14:19,258 --> 00:14:22,693
you just say to                 
the CMSensorRecorder.           

309
00:14:22,762 --> 00:14:24,795
Record accelerometer for        
some duration,                  

310
00:14:24,864 --> 00:14:26,564
and it will start               
recording it, okay, and         

311
00:14:26,633 --> 00:14:27,765
you can say whatever            
the duration is.                

312
00:14:27,833 --> 00:14:30,935
Now, I recommend keeping that   
duration as short as makes      

313
00:14:31,003 --> 00:14:34,072
sense for your app, okay,       
[LAUGH] whatever is going on.   

314
00:14:34,140 --> 00:14:37,408
It's expensive to turn that     
accelerometer on and record.    

315
00:14:37,477 --> 00:14:39,276
However, this is                
really in a way,                

316
00:14:39,345 --> 00:14:42,613
less expensive than doing some  
other things, because this,     

317
00:14:42,681 --> 00:14:45,716
most iOS devices, in fact,      
probably all of them that can   

318
00:14:45,785 --> 00:14:48,719
implement this, they know       
how to go to sleep, right?      

319
00:14:48,788 --> 00:14:50,521
The screen turns black,         
they're asleep,                 

320
00:14:50,590 --> 00:14:52,322
the processor's not             
really running.                 

321
00:14:52,391 --> 00:14:56,293
But that thing is still         
collecting accelerometer data.  

322
00:14:56,362 --> 00:14:59,396
So, they've separated out the   
accelerometer hardware into     

323
00:14:59,465 --> 00:15:01,598
a separate little chip that     
knows how to collect data, and  

324
00:15:01,667 --> 00:15:04,768
then report it back when        
the system wakes back up. So,   

325
00:15:04,837 --> 00:15:07,571
it is possible if you           
want to go for a run, and       

326
00:15:07,640 --> 00:15:11,342
your app wants to measure the   
person's acce- acceleration in  

327
00:15:11,411 --> 00:15:13,277
three dimensions while          
they are running, or            

328
00:15:13,346 --> 00:15:15,413
they put it on their arm, or    
in their pocket, or whatever.   

329
00:15:15,481 --> 00:15:18,016
And it goes to sleep, because   
it's not running your app.      

330
00:15:18,084 --> 00:15:20,251
They run for one hour and       
when they come back, and        

331
00:15:20,320 --> 00:15:22,653
then the data can all be        
there without the app having    

332
00:15:22,722 --> 00:15:25,355
to constantly run and ask for   
it, okay. There is a lot of     

333
00:15:25,424 --> 00:15:28,425
fitness API that I'm not        
talking about here [LAUGH] in   

334
00:15:28,494 --> 00:15:31,595
core motion that in that is     
same vein where you gonna ask   

335
00:15:31,664 --> 00:15:35,232
the system please record this   
things for me. And then,        

336
00:15:35,301 --> 00:15:38,969
if you get them later, you ask  
for them later. For example,    

337
00:15:39,038 --> 00:15:40,972
this quarter I didn't get to    
talk about core location.       

338
00:15:41,040 --> 00:15:43,741
Okay, core location is          
something I highly recommend    

339
00:15:43,810 --> 00:15:46,377
you look into, possibly for     
your final project. And         

340
00:15:46,446 --> 00:15:48,646
it core location can            
record your GPS,                

341
00:15:48,715 --> 00:15:51,582
or otherwise location, and      
it can do it in a way that      

342
00:15:51,650 --> 00:15:53,384
doesn't cause the phone to      
have to be awake all of         

343
00:15:53,453 --> 00:15:57,321
the time. All right, so         
once you start a recording,     

344
00:15:57,390 --> 00:15:59,524
then you can go back and        
get the recorded data.          

345
00:15:59,592 --> 00:16:02,459
It only keeps a recorded data   
I think for three days, so      

346
00:16:02,528 --> 00:16:04,362
you wanna be asking for         
it in a time,                   

347
00:16:04,430 --> 00:16:06,731
reasonably timely manner but    
you can ask for                 

348
00:16:06,799 --> 00:16:09,266
the accelerometer data          
during a certain time.          

349
00:16:09,335 --> 00:16:12,836
And it's gonna come back as     
the CMSensorDataList which      

350
00:16:12,905 --> 00:16:16,673
you just basically for in to    
get CM recorded accelerometer,  

351
00:16:16,742 --> 00:16:20,244
this would just could be that   
XYZ of all that stuff you can   

352
00:16:20,313 --> 00:16:23,747
look through there. And         
usually you gonna take that     

353
00:16:23,816 --> 00:16:27,317
list and average it or          
something like that to trying   

354
00:16:27,386 --> 00:16:30,855
to figure what's going on.      
Now if what you're doing is     

355
00:16:30,924 --> 00:16:33,891
looking at accelerometer        
data because you want to try    

356
00:16:33,960 --> 00:16:36,894
to figure out if these are      
running or staying still or     

357
00:16:36,962 --> 00:16:38,729
walking. Or                     
are they in their car?          

358
00:16:38,798 --> 00:16:41,899
Then you don't wanna use that,  
you wanna use this API, okay?   

359
00:16:41,968 --> 00:16:45,603
There's an API called Activity  
Monitoring that will use        

360
00:16:45,671 --> 00:16:49,574
a different object, here, it's  
not the CM Motion Manager,      

361
00:16:49,642 --> 00:16:53,744
it's CMMotionActivityManager,   
and it's very similar API.      

362
00:16:53,813 --> 00:16:56,413
You stay startActivityUpdates   
and you have a closure.         

363
00:16:56,482 --> 00:16:59,083
And it will call that           
periodically, telling you what  

364
00:16:59,152 --> 00:17:01,185
the user's doing.               
Are they standing still?        

365
00:17:01,254 --> 00:17:03,921
Are they walking, running, are  
they in their car, cycling?     

366
00:17:03,989 --> 00:17:06,724
This is a really powerful API,  
it's using a lot of input       

367
00:17:06,792 --> 00:17:08,926
to try and figure out           
what's going on here.           

368
00:17:08,995 --> 00:17:11,595
It's been very finely tuned,    
especially for                  

369
00:17:11,664 --> 00:17:15,266
driving because of this new Do  
Not Disturb feature in IOS 11.  

370
00:17:15,335 --> 00:17:17,235
So this is how you              
would want to try and           

371
00:17:17,303 --> 00:17:19,603
figure out what the user        
is doing rather than            

372
00:17:19,672 --> 00:17:22,072
trying to look at their         
accelerometer data and          

373
00:17:22,141 --> 00:17:24,775
figure it out, okay? This       
data is stored, I think for     

374
00:17:24,844 --> 00:17:27,378
a little longer, maybe like     
seven days, I am not sure.      

375
00:17:27,446 --> 00:17:31,415
But you can go back and look    
at this data with a from and    

376
00:17:31,484 --> 00:17:36,186
to, and again it's gonna call   
you with the information, and   

377
00:17:36,255 --> 00:17:39,589
you can get all that. Now in    
addition to that, you can also  

378
00:17:39,658 --> 00:17:42,993
get pedometer information. So   
steps, user is walking around,  

379
00:17:43,062 --> 00:17:45,963
what are they doing.            
Similar API, Start update,      

380
00:17:46,032 --> 00:17:48,832
you get a closure,              
it calls you back. Pedometer    

381
00:17:48,901 --> 00:17:51,736
information really only         
makes sense overtime, right?    

382
00:17:51,804 --> 00:17:53,604
You're not gonna ask like how   
many steps are you seeing       

383
00:17:53,672 --> 00:17:55,506
right now? Okay, you are in     
the middle of a step.           

384
00:17:55,575 --> 00:17:57,507
No, it's like how many did      
you take in the last hour,      

385
00:17:57,576 --> 00:17:59,977
have you taken the last minute  
or whatever? So when you call   

386
00:18:00,046 --> 00:18:02,513
this you get back a struct      
that has a start date and       

387
00:18:02,581 --> 00:18:05,349
an end date of the recording    
that it made and it'll tell     

388
00:18:05,418 --> 00:18:08,519
you how many steps were taken,  
how far they walked. How many   

389
00:18:08,588 --> 00:18:11,588
floors they went up and         
down, stuff like that, okay?    

390
00:18:11,657 --> 00:18:13,891
So pedometer, if you're doing   
some kind of fitness app or     

391
00:18:13,960 --> 00:18:15,960
something like that, a          
pedometer is a cool thing for   

392
00:18:16,028 --> 00:18:19,162
that. You can also find out     
Altimeter, okay? Now this is    

393
00:18:19,231 --> 00:18:22,166
relative Altimeter, it can't    
tell you exactly what your      

394
00:18:22,235 --> 00:18:24,802
altitude is, because            
really it's just measuring      

395
00:18:24,870 --> 00:18:27,972
the barometric pressure around  
you. But as you go up and       

396
00:18:28,040 --> 00:18:31,675
down, of course that pressure   
is going to change and so       

397
00:18:31,744 --> 00:18:35,312
it can give you a relative      
altitude change. Okay, now,     

398
00:18:35,381 --> 00:18:37,881
let me talk a little bit        
about authorization for         

399
00:18:37,950 --> 00:18:40,751
all this stuff. Some of         
the information here that we    

400
00:18:40,820 --> 00:18:43,554
talking about is considered     
private to the user.            

401
00:18:43,623 --> 00:18:46,624
Like their steps information    
and what they are doing,        

402
00:18:46,693 --> 00:18:50,061
standing still, driving,        
that's private information.     

403
00:18:50,129 --> 00:18:52,996
So if you wanna get that        
information the system is       

404
00:18:53,065 --> 00:18:56,400
going to ask the user is it     
okay to share this information  

405
00:18:56,468 --> 00:18:59,970
with this app? And they're      
gonna say yes or no. So you if  

406
00:19:00,039 --> 00:19:03,074
you are gonna use this private  
information you need to check   

407
00:19:03,142 --> 00:19:05,709
the AuthorizationStatus         
before you go and try and       

408
00:19:05,778 --> 00:19:08,579
access this data. Otherwise     
it's just gonna fail and        

409
00:19:08,648 --> 00:19:11,282
give you an error that          
explains it, but this way you   

410
00:19:11,350 --> 00:19:13,984
can avoid even wasting your     
time calling that. And          

411
00:19:14,053 --> 00:19:16,720
here's the authorization        
statuses you can get.           

412
00:19:16,789 --> 00:19:19,657
You can have notDetermined,     
the user hasn't been asked      

413
00:19:19,725 --> 00:19:22,926
yet, okay? So we don't know     
what it is. Restricted means    

414
00:19:22,995 --> 00:19:26,530
the user can't be asked,        
okay, about this.               

415
00:19:26,598 --> 00:19:29,533
Maybe because they've just      
turned off fitness tracking in  

416
00:19:29,602 --> 00:19:32,502
their phone in their Privacy    
Settings so they're not gonna   

417
00:19:32,571 --> 00:19:34,872
have you ask because this       
user just told me no.           

418
00:19:34,941 --> 00:19:37,541
No apps can do any of           
this fitness data.              

419
00:19:37,609 --> 00:19:40,110
Or it's either Denied or        
Authorized if they've been      

420
00:19:40,179 --> 00:19:42,813
asked okay what their answer    
is. And of course they can go   

421
00:19:42,882 --> 00:19:45,149
back and change this in         
their settings, right?          

422
00:19:45,218 --> 00:19:47,451
So if you have an app and       
it depends on this,             

423
00:19:47,520 --> 00:19:50,287
and you can check this,         
it says Denied, you can put up  

424
00:19:50,355 --> 00:19:53,256
an alert that says, you denied  
me the access to do this,       

425
00:19:53,325 --> 00:19:56,927
so I can't do this feature.     
If you wanna re-enable it,      

426
00:19:56,996 --> 00:20:00,630
go to Settings and do it,       
all right? Okay, so the demo    

427
00:20:00,699 --> 00:20:03,601
I'm gonna do is a super little  
simple one. I'm not even gonna  

428
00:20:03,669 --> 00:20:05,902
use device motion, I'm just     
gonna use the accelerometer.    

429
00:20:05,971 --> 00:20:08,039
We're gonna take our            
Playing Card app,               

430
00:20:08,107 --> 00:20:10,441
if you remember that app        
from many weeks ago.            

431
00:20:10,509 --> 00:20:12,042
And remember it has             
the cards flying around?        

432
00:20:12,111 --> 00:20:16,012
Here, let's actually go and     
run it, here it is,             

433
00:20:16,081 --> 00:20:19,883
I'm gonna run it on my iPad     
over here. So here it is,       

434
00:20:19,952 --> 00:20:23,520
remember this app right here?   
I got the cards here and        

435
00:20:23,589 --> 00:20:28,058
I got my iPad here, tapping on  
it. I've got match in the very  

436
00:20:28,127 --> 00:20:31,461
first cards. So what we're      
gonna do is make it so          

437
00:20:31,530 --> 00:20:36,000
that these cards are affected   
by gravity, real gravity okay?  

438
00:20:36,068 --> 00:20:37,167
We're gonna make it so          

439
00:20:37,236 --> 00:20:40,338
that the cards go towards the   
center of the earth basically.  

440
00:20:40,406 --> 00:20:42,239
And we're gonna do that         
with the accelerometer and      

441
00:20:42,308 --> 00:20:43,841
measure the acceleration        
due to gravity.                 

442
00:20:43,910 --> 00:20:46,343
Now, again, I'm not gonna       
use device motion so            

443
00:20:46,412 --> 00:20:47,945
if I shake my, my iPad around,  

444
00:20:48,014 --> 00:20:50,347
it's, they're gonna             
start flying around.            

445
00:20:50,416 --> 00:20:53,784
And not too fast, because it's  
just acceleration. It's not     

446
00:20:53,852 --> 00:20:56,920
actual motion. But so, we're    
not gonna worry about that,     

447
00:20:56,989 --> 00:20:59,156
okay? If I didn't want that,    
which I probably wouldn't,      

448
00:20:59,225 --> 00:21:00,757
then we'd use devi-,            
device motion. But              

449
00:21:00,826 --> 00:21:03,394
we're trying to save time, cuz  
we got a lot to demo today.     

450
00:21:03,463 --> 00:21:07,564
So we're just gonna use         
accelerometer. So let's jump    

451
00:21:07,633 --> 00:21:11,868
back here into Playing Card,    
you all remember it here.       

452
00:21:11,937 --> 00:21:14,138
We got this pile of             
Playing Card here.              

453
00:21:14,207 --> 00:21:15,839
So how are we gonna do this?    

454
00:21:15,908 --> 00:21:18,209
How are we gonna be make our    
cards be affected by gravity?   

455
00:21:18,277 --> 00:21:20,577
Well, it turns out that         
there's a behavior.             

456
00:21:20,646 --> 00:21:23,614
One of the animation behaviors  
is gravity behavior and         

457
00:21:23,683 --> 00:21:26,550
you can specify the magnitude   
and the direction that          

458
00:21:26,619 --> 00:21:30,087
the gravity is coming from,     
okay? And so what I'm gonna do  

459
00:21:30,156 --> 00:21:33,524
is as my device tilts around,   
I'm gonna change where          

460
00:21:33,592 --> 00:21:36,626
gravity is so that it goes      
towards of the center of        

461
00:21:36,695 --> 00:21:39,296
the Earth. And that's really    
easy to do in Playing Card      

462
00:21:39,364 --> 00:21:41,532
because we already have         
this card behavior, right?      

463
00:21:41,600 --> 00:21:44,568
Remember this sub class         
of UIDynamicBehavior            

464
00:21:44,637 --> 00:21:48,138
that handles our collisions     
like do we allow rotation,      

465
00:21:48,207 --> 00:21:51,908
when we push an item, etc.,     
and we just added those things  

466
00:21:51,977 --> 00:21:54,811
as our child behavior. So I'm   
gonna do exact same thing for   

467
00:21:54,880 --> 00:21:58,883
gravity. So I'm gonna create a  
new behavior, gonna call it my  

468
00:21:58,951 --> 00:22:03,187
gravityBehavior, it's gonna     
be a UIGravityBehavior. And     

469
00:22:03,255 --> 00:22:06,089
I'm actually gonna initialize   
it in exactly the same way      

470
00:22:06,158 --> 00:22:08,959
that I did these other ones up  
here we just use a closure,     

471
00:22:09,028 --> 00:22:12,730
right? I'm gonna execute        
a closure to initialize them.   

472
00:22:12,798 --> 00:22:17,668
So here I'm gonna let behavior  
equal a UIGravityBehavior.      

473
00:22:17,737 --> 00:22:22,139
Now the only initialization     
I'm gonna do at the start here  

474
00:22:22,207 --> 00:22:26,076
is to set the magnitude of      
the gravity to 0, okay?         

475
00:22:26,145 --> 00:22:28,545
Now you can even control what   
the magnitude of the gravity,   

476
00:22:28,614 --> 00:22:29,647
and remember this is not,       

477
00:22:29,715 --> 00:22:32,282
we're not talking about real    
gravity here. We're talking     

478
00:22:32,351 --> 00:22:35,252
about the gravity that affects  
the animation of these items,   

479
00:22:35,321 --> 00:22:37,421
right? So you can set that      
to anything you want, okay?     

480
00:22:37,489 --> 00:22:39,990
Whatever gravity you want.      
So I'm gonna set it to 0, and   

481
00:22:40,059 --> 00:22:42,026
the reason for that is          
remember I said that we don't   

482
00:22:42,094 --> 00:22:44,361
want to turn the accelerometer  
on until we're on screen.       

483
00:22:44,430 --> 00:22:46,296
And as soon as we go off        
screen we're going to turn it   

484
00:22:46,365 --> 00:22:48,265
off, cuz we don't want          
the accelerometer on. So        

485
00:22:48,334 --> 00:22:51,868
until I turn the accelerometer  
on, I want no gravity to be     

486
00:22:51,937 --> 00:22:55,639
affecting my cards. So they'll  
just do what they normally do   

487
00:22:55,708 --> 00:22:58,943
until I turn, until I hook      
it up to the accelerometer.     

488
00:22:59,011 --> 00:23:02,313
All right? So there's our       
behavior. Now, anytime we have  

489
00:23:02,381 --> 00:23:05,949
a child behavior like this,     
we're gonna wanna make sure     

490
00:23:06,018 --> 00:23:09,419
that new items that we add to   
it are added so that gravity    

491
00:23:09,488 --> 00:23:12,923
effects them. And of course     
if when we remove an item,      

492
00:23:12,992 --> 00:23:20,363
we want the gravity to          
stop affecting them. Oops!      

493
00:23:20,432 --> 00:23:25,235
And we always need to add any   
of these behaviors as a child   

494
00:23:25,304 --> 00:23:31,342
behavior like this. Okay,       
so now, our cardBehavior,       

495
00:23:31,410 --> 00:23:37,748
up here, That we defined        
up here. Now, in addition       

496
00:23:37,816 --> 00:23:40,751
to doing collisions and having  
this other item behavior,       

497
00:23:40,820 --> 00:23:43,420
and being able to be pushed     
and all that, it's also         

498
00:23:43,489 --> 00:23:46,357
affected by gravity which       
starts out zero. Okay, so       

499
00:23:46,425 --> 00:23:50,594
now that we can do that, let's  
go back to our controller,      

500
00:23:50,663 --> 00:23:53,263
this is our viewController      
where we make all the cards     

501
00:23:53,331 --> 00:23:55,899
and all that stuff. And it      
knows about the card behavior.  

502
00:23:55,968 --> 00:24:00,537
And I'm going to turn on the    
accelerometer when we appear,   

503
00:24:00,606 --> 00:24:03,040
and I'm gonna turn it off       
when we disappear. And          

504
00:24:03,108 --> 00:24:06,409
when I turn it on, all I'm      
gonna do is register a closure  

505
00:24:06,478 --> 00:24:08,946
that takes                      
the accelerometer's data and    

506
00:24:09,015 --> 00:24:11,982
puts it into that               
cardBehavior's data, right?     

507
00:24:12,050 --> 00:24:18,354
So let's do that. I'm just      
gonna first do viewDidAppear,   

508
00:24:18,423 --> 00:24:22,326
okay? super.viewDidAppear,      

509
00:24:22,395 --> 00:24:26,196
animated, all right?            
And so, in viewDidAppear,       

510
00:24:26,265 --> 00:24:29,366
the very first thing I'm gonna  
do is figure out how to get     

511
00:24:29,435 --> 00:24:33,904
my, motion manager going on     
here. And the way that I'm      

512
00:24:33,973 --> 00:24:38,142
going to do that,               
is by creating a shared one,    

513
00:24:38,210 --> 00:24:40,744
because really I can only       
have one, as we talked about,   

514
00:24:40,813 --> 00:24:44,014
motion manager per app.         
It only makes sense to do one.  

515
00:24:44,083 --> 00:24:46,550
So I'm gonna do that            
actually in another file and    

516
00:24:46,619 --> 00:24:49,420
I want to show you a little     
bit how what kind of what the,  

517
00:24:49,488 --> 00:24:52,088
conventions we might use        
are to create something on      

518
00:24:52,157 --> 00:24:55,559
the file. Now, what I'm gonna   
create here is an extension to  

519
00:24:55,628 --> 00:24:57,794
CMMotionManager to              
add a static var,               

520
00:24:57,863 --> 00:24:59,597
which is the shared one, okay?  

521
00:24:59,665 --> 00:25:02,532
And so that's what help         
people get it. So usually,      

522
00:25:02,601 --> 00:25:06,236
we call files that have         
an extension like that.         

523
00:25:06,304 --> 00:25:09,005
The same, the name of the       
class that we're extending and  

524
00:25:09,074 --> 00:25:09,873
then plus sign, and             

525
00:25:09,942 --> 00:25:13,043
then the description of what's  
in there. In this case, it's    

526
00:25:13,112 --> 00:25:16,212
gonna be shared. A shared one,  
so I'm gonna call it shared.    

527
00:25:16,281 --> 00:25:19,116
So it's called                  
CMMotionManager+shared.         

528
00:25:19,184 --> 00:25:21,919
It doesn't wanna the import     
Foundation instead it           

529
00:25:21,987 --> 00:25:23,920
wants to import CoreMotion,     
okay?                           

530
00:25:23,989 --> 00:25:27,290
Anytime you do anything with    
CoreMotion you need to import   

531
00:25:27,359 --> 00:25:30,928
CoreMotion. So I'm just         
gonna have an extension         

532
00:25:30,996 --> 00:25:35,532
to CMMotionManager and it's     
just gonna be a static var.     

533
00:25:35,601 --> 00:25:39,202
So a class var, right,          
called shared which is,         

534
00:25:39,271 --> 00:25:43,207
is an instance of               
CMMotionManager. So now,        

535
00:25:43,275 --> 00:25:46,310
anyone who wants to use a       
MotionManager can use this one  

536
00:25:46,379 --> 00:25:48,078
right here and they'll          
all be sharing the same.        

537
00:25:48,147 --> 00:25:49,946
Now, of course,                 
our simple app,                 

538
00:25:50,015 --> 00:25:51,148
we're only using it             
in one place, but               

539
00:25:51,217 --> 00:25:54,518
I just wanna to show you, this  
is how you could do shared,     

540
00:25:54,586 --> 00:25:57,654
data if you wanted              
to in your app.                 

541
00:25:57,723 --> 00:26:01,558
All right, so viewDidAppear is  
happening here, we wanna turn   

542
00:26:01,626 --> 00:26:04,894
on the accelerometer. First     
thing we always do is what?     

543
00:26:04,963 --> 00:26:06,329
Check to make sure              
we can do it.                   

544
00:26:06,398 --> 00:26:10,300
Okay, so let's do that and say  
if the CMMotionManager, and     

545
00:26:10,369 --> 00:26:13,170
now, I'm not getting            
escape completion,              

546
00:26:13,238 --> 00:26:16,539
that's because I need to        
import CoreMotion in here       

547
00:26:16,608 --> 00:26:19,709
as well. If I'm gonna use       
CoreMotion I need to do it.     

548
00:26:19,778 --> 00:26:21,544
And now,                        
it's figuring it out for me.    

549
00:26:21,613 --> 00:26:24,714
And I'm gonna do shared and     
I'm gonna                       

550
00:26:24,783 --> 00:26:28,185
call the method there to check  
if to see if my accelerometer   

551
00:26:28,253 --> 00:26:33,023
is available called             
isAccelerometer Available. And  

552
00:26:33,092 --> 00:26:35,826
if it is available here, then   
the first thing I'm gonna do    

553
00:26:35,895 --> 00:26:38,728
is take, tell my cardBehavior   
to have it's gravityBehavior    

554
00:26:38,797 --> 00:26:40,497
turn it it magnitude            
back to 1.0.                    

555
00:26:40,566 --> 00:26:45,902
So we're gonna turn on the      
gravity in our cardBehavior.    

556
00:26:45,971 --> 00:26:48,105
Then we wanna register          
a closure with                  

557
00:26:48,173 --> 00:26:52,075
the MotionManager to call us    
with accelerometer updates.     

558
00:26:52,144 --> 00:26:55,479
And we do that by saying        
CMMotionManager.shared          

559
00:26:55,547 --> 00:26:59,115
.startAccelerometerUpdates.     
And you can see here the one    

560
00:26:59,184 --> 00:27:01,952
where you pull and here is the  
one where we get the closure.   

561
00:27:02,021 --> 00:27:03,587
So we want the one              
with the closure here.          

562
00:27:03,656 --> 00:27:06,022
We're gonna do it on            
the main queue, okay?           

563
00:27:06,091 --> 00:27:09,025
And the handler, we'll just     
double-click. And you can see   

564
00:27:09,094 --> 00:27:11,962
that handler has the argument   
here which is the data.         

565
00:27:12,030 --> 00:27:16,700
That's the AccelerometerData    
and it has a possible error,    

566
00:27:16,769 --> 00:27:20,604
which could be null,            
to use the closing trailer,     

567
00:27:20,672 --> 00:27:24,742
the trailing closure syntax     
here. Make that work.           

568
00:27:24,810 --> 00:27:26,943
So this is all we need to       
do to get these updates.        

569
00:27:27,012 --> 00:27:30,013
Now, how often are we           
gonna get these updates?        

570
00:27:30,081 --> 00:27:34,651
Well, we get to say.            
We get to say CMMotionManager   

571
00:27:34,720 --> 00:27:38,188
.accelerometer, accelerometer   
UpdateInterval,                 

572
00:27:38,257 --> 00:27:43,260
meterUpdateInterval. What is    
it called? I can't type here,   

573
00:27:43,329 --> 00:27:48,031
called acc, let's just go       
updateinterval. No? Sorry,      

574
00:27:48,100 --> 00:27:52,769
.shared.accelerometer           
UpdateInterval.                 

575
00:27:52,838 --> 00:27:55,405
And, okay, think about what's   
happening with these cards,     

576
00:27:55,474 --> 00:27:58,475
right? They're being pulled by  
gravity going on. They don't    

577
00:27:58,544 --> 00:28:01,077
need to know instantly what     
the gravity is. In fact,        

578
00:28:01,146 --> 00:28:03,780
probably once every half        
second would be enough, but     

579
00:28:03,849 --> 00:28:06,983
to be sure, I'll go maybe once  
every tenth of a second, okay?  

580
00:28:07,052 --> 00:28:09,619
It doesn't, I don't really      
do much in the closure, so      

581
00:28:09,688 --> 00:28:12,422
it's really not a performance   
hit to change that too much.    

582
00:28:12,491 --> 00:28:14,891
So we'll go about every tenth,  
we could go fifth, and          

583
00:28:14,960 --> 00:28:17,460
we could kinda tune this, we    
might find that once a second   

584
00:28:17,529 --> 00:28:19,195
is enough to get                
the behavior we want.           

585
00:28:19,264 --> 00:28:21,598
In which case, we should        
use once per second, so         

586
00:28:21,667 --> 00:28:24,834
this is something we have to    
tune. All right, now, we wanna  

587
00:28:24,903 --> 00:28:27,971
get AccelerometerData,          
where is it? It's in here,      

588
00:28:28,040 --> 00:28:31,140
this is that struck that has    
the acceleration x, y, and z.   

589
00:28:31,209 --> 00:28:33,777
So I'm gonna say if I can       
let x, which is gonna be my     

590
00:28:33,845 --> 00:28:37,046
acceleration in x, equal        
that data? If we have it,       

591
00:28:37,115 --> 00:28:39,315
if it wasn't an error,          
acceleration.x.                 

592
00:28:39,384 --> 00:28:41,852
And I'm gonna let y =           
the data?.acceleration.y.       

593
00:28:41,920 --> 00:28:44,988
So if I'm able to get           
the information, if I can't,    

594
00:28:45,057 --> 00:28:48,124
I'll just ignore this,          
I'm gonna ignore errors.        

595
00:28:48,193 --> 00:28:50,593
I should handle them            
if I need to here, but          

596
00:28:50,662 --> 00:28:55,532
I'm gonna ignore errors.        
So if that comes through, now,  

597
00:28:55,600 --> 00:28:59,302
I need to set the gravity       
vector, okay, the direction of  

598
00:28:59,371 --> 00:29:02,272
gravity, in my CardBehavior's   
GravityBehavior. Okay, now,     

599
00:29:02,341 --> 00:29:05,876
this is an interesting          
thing here to wanna do,         

600
00:29:05,945 --> 00:29:10,313
because the AccelerometerData   
is in with respect to           

601
00:29:10,382 --> 00:29:15,385
the device, okay? If I hold     
this device up right here,      

602
00:29:15,454 --> 00:29:17,954
okay?                           
Here's the home button, down.   

603
00:29:18,023 --> 00:29:21,324
That means in the y direction   
this is gravity 1.0, okay? And  

604
00:29:21,393 --> 00:29:24,894
this will be if it is going up  
it will be negative gravity     

605
00:29:24,963 --> 00:29:28,832
right here. And this is the x   
direction and this is the z     

606
00:29:28,901 --> 00:29:34,204
direction back behind, okay?    
So that's different then        

607
00:29:34,272 --> 00:29:38,275
possibly, my reference frame    
of my animation because for     

608
00:29:38,343 --> 00:29:40,977
example, I might be rotated,    
okay?                           

609
00:29:41,046 --> 00:29:44,681
So if I'm rotated, maybe my     
app does autorotation, and so   

610
00:29:44,750 --> 00:29:48,785
up is actually the x location.  
Do you see what I'm saying?     

611
00:29:48,853 --> 00:29:53,256
So the hardware and the view    
are not quiet the same. Now,    

612
00:29:53,324 --> 00:29:55,758
before we try and               
deal with that,                 

613
00:29:55,827 --> 00:29:59,663
let's just try saying           
that the CardBehaviors's,       

614
00:29:59,731 --> 00:30:04,601
GravityBehavior's direction,    
gravityDirection is called,     

615
00:30:04,670 --> 00:30:08,605
which is a CGVector, which      
just means x and y extent,      

616
00:30:08,674 --> 00:30:13,543
right? We'll just try           
setting it to the x and         

617
00:30:13,612 --> 00:30:17,580
y of the accelerometer. Let's   
just see what happens when we   

618
00:30:17,649 --> 00:30:21,384
do that, okay? Because that     
kinda should work. Let's,       

619
00:30:21,453 --> 00:30:26,656
let's run and see what happens  
here, though. All right,        

620
00:30:26,725 --> 00:30:28,791
so, so                          
you can see what's going        

621
00:30:28,860 --> 00:30:32,061
on here on this screen, okay?   
I'll have to tell you what I'm  

622
00:30:32,130 --> 00:30:35,765
doing. So here, I'm holding my  
device now straight up, okay?   

623
00:30:35,834 --> 00:30:37,200
And you can actually see,       
look.                           

624
00:30:37,268 --> 00:30:40,403
All my cards are actually       
going up. If I turn it upside   

625
00:30:40,472 --> 00:30:43,840
down, now, they'll fall down.   
Back to the right side,         

626
00:30:43,909 --> 00:30:47,310
woo hoo, they all go back up.   
So gravity is working,          

627
00:30:47,379 --> 00:30:49,813
but it's kind of anti-grav,     
okay? It's working              

628
00:30:49,882 --> 00:30:52,449
opposite direction. Now, can    
anyone think why it's going in  

629
00:30:52,517 --> 00:30:57,187
the opposite direction and      
why? Okay, where is our origin  

630
00:30:57,255 --> 00:31:01,491
in, in our drawing thing?       
It's in the upper left, right?  

631
00:31:01,560 --> 00:31:06,129
So if we have gravity which     
is down, where is down in       

632
00:31:06,198 --> 00:31:11,034
a coordinate system where the   
upper left is 0, 0? It's up,    

633
00:31:11,103 --> 00:31:14,237
right? So up towards zero,      
zero. So that's the problem.    

634
00:31:14,305 --> 00:31:18,175
So we need to, to kind of       
reverse y because the device's  

635
00:31:18,243 --> 00:31:21,411
gravity down is different than  
our coordinate system. And      

636
00:31:21,480 --> 00:31:24,081
actually, it could work,        
it works. Right now I have my   

637
00:31:24,149 --> 00:31:27,350
orientation locked so           
as I rotate my device           

638
00:31:27,419 --> 00:31:31,020
it's not autorotating. But if   
I auto rotate it, then my view  

639
00:31:31,089 --> 00:31:34,357
would constantly be changing.   
So how are we gonna fix that?   

640
00:31:34,426 --> 00:31:38,027
Let's go back to our code over  
here. And what we're gonna do   

641
00:31:38,096 --> 00:31:41,698
is change this x and y from     
hardware coordinate system to   

642
00:31:41,766 --> 00:31:45,201
our view coordinate system and  
we're gonna do this,            

643
00:31:45,270 --> 00:31:49,606
I'm gonna have a little thing   
to type it fast here. We're     

644
00:31:49,674 --> 00:31:51,874
gonna do this depending on      
the orientation of the device.  

645
00:31:51,943 --> 00:31:54,411
So I'm switching on             
the device's orientation. So    

646
00:31:54,479 --> 00:31:57,080
remember we used UIDevice to    
see if it was an iPad. Well,    

647
00:31:57,149 --> 00:32:00,116
we can also use UIDevice to     
find out what the orientation   

648
00:32:00,185 --> 00:32:02,685
is, either portrait,            
portrait upside down,           

649
00:32:02,754 --> 00:32:05,922
that means portrait with        
the home button up on the top,  

650
00:32:05,991 --> 00:32:08,692
or landscape left or right.     
Landscape left is the home      

651
00:32:08,760 --> 00:32:12,262
button on the left,             
landscape mode. And of course,  

652
00:32:12,331 --> 00:32:16,432
these need to be VAR's and by   
the way, yes, you can say if    

653
00:32:16,501 --> 00:32:20,102
VAR x and have this be a VAR,   
that is legal. Probably,        

654
00:32:20,171 --> 00:32:22,705
maybe didn't get that when you  
read your homework part of it   

655
00:32:22,774 --> 00:32:26,342
early in the quarter, but you   
can. So,uh, if I'm in portrait  

656
00:32:26,411 --> 00:32:29,178
mode, then we've already        
seen that Y needs to be -1,     

657
00:32:29,247 --> 00:32:32,849
right? Because up is down and   
down is up. If we're in         

658
00:32:32,918 --> 00:32:35,485
portraitUpsideDown, they        
actually match up.              

659
00:32:35,554 --> 00:32:36,820
Okay, in portraitUpsideDown,    

660
00:32:36,889 --> 00:32:38,188
the home button is              
at the top and so               

661
00:32:38,256 --> 00:32:40,590
is our coordinate system. So    
we're all in good shape. And    

662
00:32:40,659 --> 00:32:42,626
landscapeLeft and               
right, actually x and           

663
00:32:42,694 --> 00:32:45,061
y have been swapped.            
Okay, cuz in landscape,         

664
00:32:45,130 --> 00:32:49,899
it's the x part of the device   
that is now the vertical, so    

665
00:32:49,968 --> 00:32:51,834
we'll have to swap them.        
And in landscapeLeft,           

666
00:32:51,903 --> 00:32:54,470
we swapped them and             
it's upside down as well. So    

667
00:32:54,539 --> 00:32:59,809
let's go see this in action.    
And we're currently locked to   

668
00:32:59,878 --> 00:33:02,646
portrait. Okay, first of all,   
now I have my device on me,     

669
00:33:02,715 --> 00:33:06,149
this up here.                   
So now my device is flat,       

670
00:33:06,218 --> 00:33:09,085
okay, so acceleration is in     
the z direction, so x and       

671
00:33:09,154 --> 00:33:12,321
y are 0. So you can see it's    
just doing it's normal,         

672
00:33:12,390 --> 00:33:15,124
floating around business.       
Now what I'm gonna do           

673
00:33:15,193 --> 00:33:18,561
is I'm gonna tilt it up so      
the home button is down. And    

674
00:33:18,630 --> 00:33:21,865
sure enough, gravity pulls      
them all down to the bottom.    

675
00:33:21,934 --> 00:33:24,233
Now I'm gonna turn it           
upside down, okay?              

676
00:33:24,302 --> 00:33:26,569
Now gravity is pulling it       
all to the other side.          

677
00:33:26,638 --> 00:33:29,272
If you're watching on the       
screen, if you can't really,    

678
00:33:29,341 --> 00:33:31,774
understand what I'm doing,      
maybe. But now let's go to      

679
00:33:31,843 --> 00:33:37,313
landscape right, right? And     
over to landscape left, okay?   

680
00:33:37,382 --> 00:33:39,249
So it's working, gravity        
is pulling on these and         

681
00:33:39,318 --> 00:33:40,884
they're still bouncing          
off each other and              

682
00:33:40,952 --> 00:33:44,153
have those forces as well.      
But they're doing that.         

683
00:33:44,222 --> 00:33:47,424
Now I'm gonna unlock my,        
rotation here,                  

684
00:33:47,492 --> 00:33:51,595
I'm gonna go swipe, turn this   
lock off and go back. Now       

685
00:33:51,663 --> 00:33:55,832
it's gonna auto rotate. Okay,   
so here we're in portrait       

686
00:33:55,900 --> 00:33:58,835
mode and these all go to the    
bottom and now if I go flat,    

687
00:33:58,903 --> 00:34:02,805
for example, in all my. So      
let's actually go here and get  

688
00:34:02,874 --> 00:34:06,042
these things loading a little   
bit. And if I go to landscape,  

689
00:34:06,111 --> 00:34:09,145
you can see that they           
stay at the bottom, okay.       

690
00:34:09,214 --> 00:34:10,680
So they're staying              
down at the bottom,             

691
00:34:10,749 --> 00:34:13,350
no matter which way I go.       
So even though my coordinate    

692
00:34:13,418 --> 00:34:16,019
system is changing here         
because I'm auto-rotating,      

693
00:34:16,087 --> 00:34:19,756
it's always knowing             
which way is down. Okay,        

694
00:34:19,824 --> 00:34:24,294
makes sense? All right, go      
back go back to blocked here.   

695
00:34:28,733 --> 00:34:31,435
Here we go, so now we can see   
it going in other directions.   

696
00:34:35,006 --> 00:34:39,876
All right, now, one other       
thing we have to do here        

697
00:34:39,944 --> 00:34:45,081
back in our code is turn        
off accelerometer updates,      

698
00:34:45,150 --> 00:34:48,251
okay? Cuz we always want,       
every time we turn it on,       

699
00:34:48,319 --> 00:34:50,454
think of somewhere where it     
makes sense to turn it off.     

700
00:34:50,522 --> 00:34:52,456
In our case, it's really        
easy where that is.             

701
00:34:52,524 --> 00:34:55,525
That's going to be in           
viewWillDisappear. So           

702
00:34:55,593 --> 00:35:00,396
let's go to viewWillDisappear.  
Super, whoops,                  

703
00:35:00,465 --> 00:35:04,968
super.viewWillDisappear.        

704
00:35:05,037 --> 00:35:06,536
And here,                       
we're gonna do two things,      

705
00:35:06,604 --> 00:35:10,173
I'm going to tell my card       
behaviors gravity behavior to   

706
00:35:10,242 --> 00:35:15,512
set it's magnitude to 0, okay?  
So stop doing gravity,          

707
00:35:15,581 --> 00:35:18,848
and I'm also going to           
tell my CMMotionManager,        

708
00:35:18,917 --> 00:35:23,687
the shared one, to stop         
accelerometer updates. Okay,    

709
00:35:23,755 --> 00:35:26,656
so you see how I've paired      
starting it with stopping it.   

710
00:35:26,725 --> 00:35:31,461
Always start and stop.          
Okay, that is it.               

711
00:35:31,530 --> 00:35:37,434
Let's go back to our            
slides here, And                

712
00:35:37,502 --> 00:35:40,470
talk about our next topic       
which is the camera and         

713
00:35:40,539 --> 00:35:43,306
the photo library               
actually as well.               

714
00:35:43,375 --> 00:35:47,943
And this API for doing this     
is actually very simple.        

715
00:35:48,012 --> 00:35:51,314
Its just a modal view control   
that you get from iOS and you   

716
00:35:51,383 --> 00:35:55,518
present it modaly that's as     
simple as that. The usage here  

717
00:35:55,587 --> 00:35:58,954
is that you're gonna create     
it, kinda configure it, set it  

718
00:35:59,023 --> 00:36:01,257
to delegate because it won't    
work without the delegate,      

719
00:36:01,326 --> 00:36:04,494
that's how it tells you what    
the photo it took was. And      

720
00:36:04,563 --> 00:36:07,130
then you present it and then    
listen to the delegate methods  

721
00:36:07,199 --> 00:36:08,097
that get's sent to you.         

722
00:36:08,166 --> 00:36:10,767
So, it's actually very simple,  
to use the camera.              

723
00:36:10,835 --> 00:36:13,236
What the user can do,           
by the way,                     

724
00:36:13,304 --> 00:36:17,239
with the camera depends on      
the platform, all right.        

725
00:36:17,308 --> 00:36:20,309
Newer devices have really       
awesome cameras, both front     

726
00:36:20,378 --> 00:36:23,613
and back, for example, with     
flash and all these things but  

727
00:36:23,682 --> 00:36:26,549
older devices don't. So         
just like we did when we did    

728
00:36:26,617 --> 00:36:30,486
Core Motion, we're gonna wanna  
ask what's available? Now,      

729
00:36:30,555 --> 00:36:33,289
what's interesting is with      
the same view controller,       

730
00:36:33,358 --> 00:36:35,391
you can ask for                 
a picture from the camera but   

731
00:36:35,460 --> 00:36:38,361
you can also ask for a picture  
from the user's photo library   

732
00:36:38,430 --> 00:36:40,163
or from their camera roll,      
right.                          

733
00:36:40,231 --> 00:36:43,533
The camera roll is where kinda  
of recently taken photos,       

734
00:36:43,602 --> 00:36:47,103
get dropped in. So the same     
view control can kind of        

735
00:36:47,171 --> 00:36:49,539
do those different things but   
they are different.             

736
00:36:49,608 --> 00:36:52,208
Okay, the UIs of them are, are  
quite different actually and    

737
00:36:52,277 --> 00:36:55,912
we'll talk about                
that in a second. So            

738
00:36:55,980 --> 00:37:00,984
not every particular, camera    
can do every type of media.     

739
00:37:01,053 --> 00:37:04,053
So, not every camera for        
example can do video.           

740
00:37:04,122 --> 00:37:07,457
Not every camera can do live    
photo. Everyone know live       

741
00:37:07,525 --> 00:37:10,760
photo is? That's like where     
you take a burst of images,     

742
00:37:10,829 --> 00:37:14,097
around the time you, you say    
picture. So you kinda have to   

743
00:37:14,165 --> 00:37:17,667
ask, is this media type         
available for this source,      

744
00:37:17,736 --> 00:37:20,670
usually the camera.             
Okay, and you do that here.     

745
00:37:20,739 --> 00:37:24,407
Now these media types           
are really unfortunately        

746
00:37:24,475 --> 00:37:28,778
this weird type here kUTType    
something which is not even     

747
00:37:28,847 --> 00:37:31,848
a string. It's a cfstring       
it turns out and                

748
00:37:31,916 --> 00:37:35,852
that does not automatically     
bridge like a nsstring does.    

749
00:37:35,921 --> 00:37:39,088
And they're defined in          
MobileCoreServices which means  

750
00:37:39,156 --> 00:37:42,658
to use camera you have to       
import MobileCoreServices. And  

751
00:37:42,727 --> 00:37:46,729
you have to use these and cast  
them to a string, okay? So,     

752
00:37:46,798 --> 00:37:49,065
sorry about that.               
I didn't write this API,        

753
00:37:49,134 --> 00:37:52,402
so we'll see, hope they         
fix that in the future,         

754
00:37:52,471 --> 00:37:54,937
but it's a little annoying.     

755
00:37:55,006 --> 00:37:57,973
You can also find out things    
about, particular camera        

756
00:37:58,042 --> 00:38:00,310
devices like, do they have      
flash and things like that,     

757
00:38:00,379 --> 00:38:02,678
that's all part of              
the UIImagePickerController.    

758
00:38:02,747 --> 00:38:04,814
Notice that all these           
methods are static funks.       

759
00:38:04,883 --> 00:38:08,451
You don't even have to create   
a UIImagePickerController to    

760
00:38:08,520 --> 00:38:10,954
do it, you can just ask         
the UIImagePickerClass          

761
00:38:11,022 --> 00:38:14,690
about these things. So here's   
kinda collecting all that       

762
00:38:14,759 --> 00:38:18,561
into some code that would put   
up a picker to capture video.   

763
00:38:18,630 --> 00:38:21,364
All right, so the first thing   
we're gonna do there is create  

764
00:38:21,432 --> 00:38:23,766
an ImagePickerController        
called picker, okay.            

765
00:38:23,835 --> 00:38:27,403
Then I'm gonna set the type     
that I want to be movie.        

766
00:38:27,472 --> 00:38:30,673
I'm gonna create a little       
local variable media type       

767
00:38:30,742 --> 00:38:33,610
movie which is that weird       
kuTTypeMovie thing as           

768
00:38:33,678 --> 00:38:34,744
a string, okay.                 

769
00:38:34,812 --> 00:38:37,613
Now I'm gonna set myself        
to be the picker delegate.      

770
00:38:37,682 --> 00:38:41,184
If I don't do that, I'll never  
find out what photo was taken.  

771
00:38:41,253 --> 00:38:43,586
So I have to do that,           
it's an absolute requirement.   

772
00:38:43,655 --> 00:38:45,654
Then I'm gonna ask you why      
ImagePickerController,          

773
00:38:45,723 --> 00:38:49,526
by the way I say UIIPC because  
it just won't fit on the slide  

774
00:38:49,594 --> 00:38:52,928
someplace. So imagine that      
says UIImagePickerController.   

775
00:38:52,997 --> 00:38:55,064
That is source type available,  
camera.                         

776
00:38:55,133 --> 00:38:57,600
So I'm gonna see is there       
a camera available on this      

777
00:38:57,669 --> 00:39:00,803
device, which for               
most things there is a camera.  

778
00:39:00,872 --> 00:39:03,139
The simulator however,          
will not have a camera so       

779
00:39:03,208 --> 00:39:06,108
this is a good way to           
test this line of code.         

780
00:39:06,177 --> 00:39:08,744
Then I'm gonna set, if it does  
have a camera, I'm gonna set    

781
00:39:08,813 --> 00:39:11,080
the source type of the picker   
to be the camera. Okay,         

782
00:39:11,149 --> 00:39:13,415
don't forget to set the source  
type where you wanna do it.     

783
00:39:13,484 --> 00:39:16,286
Now, this source type is where  
you would say photo library if  

784
00:39:16,354 --> 00:39:18,788
you wanted to let the user      
choose a photo from the photo   

785
00:39:18,856 --> 00:39:23,292
library instead, okay,          
or the camera roll. So          

786
00:39:23,361 --> 00:39:27,530
then we're gonna say, tell me   
the available media types for   

787
00:39:27,599 --> 00:39:31,067
that source, camera or          
whatever source type that I'm   

788
00:39:31,136 --> 00:39:34,070
using. And I'm gonna look in    
the array that comes back and   

789
00:39:34,138 --> 00:39:38,307
see if movies, kUTType movie,   
is in there. And if it is,      

790
00:39:38,376 --> 00:39:42,811
I'm ready to go. I'm gonna set  
my media types to be movie and  

791
00:39:42,880 --> 00:39:44,179
then we're gonna put            
the picker up. So               

792
00:39:44,248 --> 00:39:48,284
this is how you put a picker    
on the screen. All right?       

793
00:39:48,353 --> 00:39:51,721
Now when I, I told you earlier  
that you can configure this     

794
00:39:51,789 --> 00:39:55,457
picker, okay, to, when          
you're putting it on screen.    

795
00:39:55,526 --> 00:39:56,559
What are some of                
the things you can do?          

796
00:39:56,628 --> 00:39:59,295
Well, you can just say          
that it allows editing.         

797
00:39:59,364 --> 00:40:01,930
So, in that sense the user      
can take a photo and            

798
00:40:01,999 --> 00:40:03,766
then even before it             
comes back to you,              

799
00:40:03,835 --> 00:40:07,337
they can zoom in on it          
a little, move around. Video,   

800
00:40:07,405 --> 00:40:10,372
they can even edit the video    
before it returns to you. So    

801
00:40:10,441 --> 00:40:13,743
you're basically has in place   
editing right in the UI,        

802
00:40:13,812 --> 00:40:17,446
the UIImagePickerController,    
puts up, which is kinda cool.   

803
00:40:17,515 --> 00:40:20,482
You can, if you're doing        
video, you can limit the video  

804
00:40:20,551 --> 00:40:23,219
capture to a certain number     
of minutes or to a certain      

805
00:40:23,288 --> 00:40:28,358
quality using these VARs right  
here. To present the picker,    

806
00:40:28,426 --> 00:40:31,027
all you do is use the same      
present modally that we did to  

807
00:40:31,095 --> 00:40:34,163
do a UI alert controller, or    
the same thing we did to put    

808
00:40:34,231 --> 00:40:37,600
our document up in Emoji art.   
And here's where you want       

809
00:40:37,669 --> 00:40:40,402
to think a little bit about     
the platform you're on.         

810
00:40:40,471 --> 00:40:44,506
Because an iPad, if you're      
gonna put the camera up, it     

811
00:40:44,575 --> 00:40:48,311
needs to be full screen modal.  
You cannot put it in a popover  

812
00:40:48,379 --> 00:40:51,447
if it's the camera, okay?       
Don't put it in a form sheet,   

813
00:40:51,516 --> 00:40:53,850
don't put it in a page sheet,   
full screen modal, okay?        

814
00:40:53,919 --> 00:40:56,418
That's actually on              
both iPad and iPhone.           

815
00:40:56,487 --> 00:41:00,022
On the iPad for the photo       
library, or the photos app,     

816
00:41:00,091 --> 00:41:04,661
you want to put in a popover,   
okay? And then on the iPhone,   

817
00:41:04,729 --> 00:41:06,695
it's gonna be full screen       
always on the iPhone, okay? So  

818
00:41:06,764 --> 00:41:10,166
just clear about, I just want   
to take a moment to make sure   

819
00:41:10,235 --> 00:41:13,803
that sinks in. On iPad, full    
screen for the camera, popover  

820
00:41:13,872 --> 00:41:16,739
for the photo library, okay?    
So if you had an app where you  

821
00:41:16,808 --> 00:41:19,241
could pick your image either    
from a camera or from a photo   

822
00:41:19,310 --> 00:41:21,544
library on the iPad, you'd      
have to have two buttons.       

823
00:41:21,612 --> 00:41:23,046
One that brought                
up the camera and               

824
00:41:23,114 --> 00:41:27,216
one that brings up the photo    
library in a popover. Okay,     

825
00:41:27,285 --> 00:41:29,786
once the thing has              
been presented and              

826
00:41:29,854 --> 00:41:33,389
the user picks and possibly     
edits their photo then          

827
00:41:33,458 --> 00:41:35,725
the delegate method             
will be called,                 

828
00:41:35,793 --> 00:41:39,762
saying that it did finish       
picking media with info, okay?  

829
00:41:39,831 --> 00:41:42,732
And this info is a dictionary,  
and inside that dictionary is   

830
00:41:42,801 --> 00:41:44,967
all the information about       
what was picked. Okay, and      

831
00:41:45,036 --> 00:41:48,204
we're gonna talk about what     
all that is on the next slide   

832
00:41:48,273 --> 00:41:50,539
but this is how you get         
the information. Now,           

833
00:41:50,608 --> 00:41:51,807
once you've got all             
the information,                

834
00:41:51,876 --> 00:41:55,277
you're going to dismiss         
your view controller, okay?     

835
00:41:55,346 --> 00:41:56,845
This is actually                
old slide here,                 

836
00:41:56,914 --> 00:41:59,582
that's just called dismiss      
not dismiss view controller     

837
00:41:59,651 --> 00:42:02,985
animated [LAUGH] right there.   
And so similarly,               

838
00:42:03,054 --> 00:42:04,854
if the user went to             
take a picture and              

839
00:42:04,922 --> 00:42:07,757
said cancel, then you're        
gonna get the dele method,      

840
00:42:07,825 --> 00:42:10,826
delegate method, imagePicture   
ControllerDidCancel.            

841
00:42:10,895 --> 00:42:13,429
And you're gonna do             
picker.presentingView           

842
00:42:13,498 --> 00:42:16,098
Controller?.dismiss, okay?      
So let's look                   

843
00:42:16,167 --> 00:42:19,068
at that dictionary, that info   
dictionary that comes along     

844
00:42:19,137 --> 00:42:21,337
with didFinishPicking           
MediaWithInfo and               

845
00:42:21,406 --> 00:42:24,106
see what we can get from this   
UI image picker UI that lets    

846
00:42:24,175 --> 00:42:26,776
the user take a picture with    
the camera or do the photo      

847
00:42:26,845 --> 00:42:30,113
library. So you're gonna find,  
there's one thing that          

848
00:42:30,181 --> 00:42:33,315
tells you what was chosen,      
image or a movie.               

849
00:42:33,384 --> 00:42:35,984
Then if it's an image, you're   
gonna have both the original    

850
00:42:36,053 --> 00:42:38,654
image that was taken and        
also the edited image if they   

851
00:42:38,723 --> 00:42:42,591
edited it. And those are just   
UI images, all right,           

852
00:42:42,660 --> 00:42:45,528
then there's Image URL,         
that's the URL for the image.   

853
00:42:45,596 --> 00:42:47,363
By the way, that is in          
a temporary location,           

854
00:42:47,432 --> 00:42:50,365
make sure you move it to        
somewhere, you know, in your    

855
00:42:50,434 --> 00:42:54,103
sandbox that's more permanent   
if you want to keep it.         

856
00:42:54,172 --> 00:42:57,072
CropRect will tell you what     
rectangle the user cropped it   

857
00:42:57,141 --> 00:42:59,542
to, if you allow editing,       
they can crop it                

858
00:42:59,611 --> 00:43:02,211
to a certain rectangle, you     
can find that out. You can get  

859
00:43:02,280 --> 00:43:05,080
some metadata about             
the media that was chosen,      

860
00:43:05,149 --> 00:43:07,183
maybe the GPS location          
that you're at,                 

861
00:43:07,252 --> 00:43:11,287
if the user allows that to be   
captured, things like that.     

862
00:43:11,356 --> 00:43:14,123
If it was a live photo that     
they took, then you get         

863
00:43:14,192 --> 00:43:17,460
a PHLivePhoto object in there.  
I'm not gonna talk about        

864
00:43:17,528 --> 00:43:21,497
the photo library framework     
which is PH stuff but           

865
00:43:21,566 --> 00:43:24,734
you can get that. Also PHAsset  
which is just a struct          

866
00:43:24,802 --> 00:43:27,270
that kind of describes the      
photo, but it doesn't actually  

867
00:43:27,339 --> 00:43:29,705
have the image.                 
You can then use it with        

868
00:43:29,774 --> 00:43:31,374
the photo library to            
get the image data.             

869
00:43:31,443 --> 00:43:34,509
And if you have video,          
then you get a MediaURL,        

870
00:43:34,578 --> 00:43:37,446
which is just a URL to a file   
in your sandbox that contains   

871
00:43:37,515 --> 00:43:40,583
the video that was captured,    
all right? So                   

872
00:43:40,652 --> 00:43:44,220
that's what you get back from   
the UIImagePickerController.    

873
00:43:45,690 --> 00:43:47,122
Now when you get                
this image back,                

874
00:43:47,191 --> 00:43:48,490
if you get an image not         
a video, if you get an image,   

875
00:43:48,559 --> 00:43:51,928
you might want to save it to    
the camera roll. Okay, now it   

876
00:43:51,996 --> 00:43:53,896
totally depends on why you're   
asking them for an image.       

877
00:43:53,965 --> 00:43:57,132
If it's purely for your app's   
purposes, maybe not but         

878
00:43:57,201 --> 00:44:00,336
if it's something where it's,   
you're like a camera app of     

879
00:44:00,404 --> 00:44:03,539
some sort. And you want, it's   
a photo that they might be      

880
00:44:03,608 --> 00:44:06,442
interested in using in other    
circumstances then you can      

881
00:44:06,510 --> 00:44:08,978
save it using this write        
image write to save photo,      

882
00:44:09,047 --> 00:44:10,979
so unfortunately,               
this is asynchronous.           

883
00:44:11,048 --> 00:44:13,616
Unfortunately, it doesn't       
use a closure API, instead,     

884
00:44:13,684 --> 00:44:15,618
it has a kind of target and     
selector, right?                

885
00:44:15,687 --> 00:44:17,686
So the callback is a target     
and a selector but              

886
00:44:17,755 --> 00:44:20,289
it's essentially, you can kind  
of imagine what this would be   

887
00:44:20,358 --> 00:44:22,992
like if it had a nice           
closure that called you back.   

888
00:44:23,060 --> 00:44:24,076
asynchronous is the image       
might be quite large. In fact,  

889
00:44:24,077 --> 00:44:25,093
And the reason it's             

890
00:44:25,162 --> 00:44:27,930
some of the cameras have very   
good cameras that are very      

891
00:44:27,999 --> 00:44:31,166
large, intra, you, you know,    
megabyte sized, images.         

892
00:44:31,235 --> 00:44:32,568
And then you talk               
about a live photo,             

893
00:44:32,637 --> 00:44:37,540
you're talking about really     
large images. Now, when you're  

894
00:44:37,608 --> 00:44:40,976
talking about saving photos,    
if you're really an app that    

895
00:44:41,045 --> 00:44:43,879
deals with photos.              
Maybe you manipulate them and   

896
00:44:43,948 --> 00:44:47,149
you have filters and things     
like that, really you're,       

897
00:44:47,217 --> 00:44:50,386
this is only just the lightest  
weight API for doing image      

898
00:44:50,455 --> 00:44:54,357
picking by the user. There's    
a whole other framework called  

899
00:44:54,425 --> 00:44:57,059
PHPhotoLibrary which            
basically is an API for         

900
00:44:57,128 --> 00:44:59,962
accessing the photos app,       
the photos that are in          

901
00:45:00,031 --> 00:45:02,698
the photos app on your phone.   
Super powerful,                 

902
00:45:02,767 --> 00:45:06,268
very highly efficient API, you  
definitely wanna check that     

903
00:45:06,337 --> 00:45:10,106
out if you're doing,            
really doing photo stuff.       

904
00:45:10,174 --> 00:45:12,942
You could of course save        
the image to your sandbox,      

905
00:45:13,011 --> 00:45:15,544
if you're just using            
the image in your own app.      

906
00:45:15,613 --> 00:45:19,448
Okay, that's perfectly legal    
as well. In addition to         

907
00:45:19,516 --> 00:45:22,651
PhPhotoLibrary as a place to    
do really cool media stuff,     

908
00:45:22,720 --> 00:45:25,754
there's also AVCaptureDevice.   
That's a whole API for          

909
00:45:25,823 --> 00:45:28,724
doing much more sophisticated   
image capture, image capture,   

910
00:45:28,793 --> 00:45:31,327
right? That you're gonna        
see when we do the demo,        

911
00:45:31,396 --> 00:45:34,664
the ImagePickerController has   
a very simple kind of camera    

912
00:45:34,732 --> 00:45:37,566
to it. So AV capture device     
let's you control a lot more    

913
00:45:37,635 --> 00:45:41,704
of the aspects of               
the photo being taken. Now,     

914
00:45:41,773 --> 00:45:43,572
what else can you do            
with the ImagePickerView?       

915
00:45:43,640 --> 00:45:47,176
It allows you to actually       
provide your own UI, even for   

916
00:45:47,244 --> 00:45:48,810
the button that                 
says Take a Photo.              

917
00:45:48,879 --> 00:45:52,214
Okay, so you get this default   
UI that is very simple,         

918
00:45:52,283 --> 00:45:55,017
it lets you take a photo and    
cancel and all that.            

919
00:45:55,086 --> 00:45:57,620
But you can actually put        
your own view on there, and     

920
00:45:57,688 --> 00:46:00,556
your view can even replace      
the existing camera controls.   

921
00:46:00,625 --> 00:46:03,625
If you say,                     
Show Camera Controls is false,  

922
00:46:03,694 --> 00:46:08,998
then yours will be the only     
UI that lays on top. The kind   

923
00:46:09,066 --> 00:46:12,468
of, what do you call it? The    
coordinate system that your     

924
00:46:12,536 --> 00:46:17,206
frame of your view is gonna     
be in is the UIScreen.main's    

925
00:46:17,275 --> 00:46:20,242
bounds, okay? So we haven't     
really talked about UIScreen,   

926
00:46:20,311 --> 00:46:23,745
it's just an object,            
it happens to have, a static    

927
00:46:23,814 --> 00:46:26,148
VAR called main. And you can    
get the bounds of that and      

928
00:46:26,217 --> 00:46:28,917
that'll tell you the bounds of  
the camera, so that you know    

929
00:46:28,986 --> 00:46:34,890
where to put your UI on top     
of that. You can also zoom or   

930
00:46:34,959 --> 00:46:37,793
translate the image that        
you£re capturing, okay, but     

931
00:46:37,862 --> 00:46:40,863
with an app line transform. So  
maybe you wanna scale it up so  

932
00:46:40,931 --> 00:46:43,399
that it is zoomed in or         
something like that,            

933
00:46:43,467 --> 00:46:46,736
you can do that. Once you       
get the image back from         

934
00:46:46,804 --> 00:46:49,939
the PickerController, you       
might want to process it, and   

935
00:46:50,007 --> 00:46:52,207
there's quite a lot of          
[LAUGH] API in iOS for          

936
00:46:52,276 --> 00:46:55,411
processing images. Most of      
it is in a framework called     

937
00:46:55,480 --> 00:46:58,914
Core Image, which I strongly    
recommend you take a look at.   

938
00:46:58,983 --> 00:47:02,718
It has literally a couple of    
hundred different filters for   

939
00:47:02,787 --> 00:47:05,488
doing blur,                     
changing the colors,            

940
00:47:05,556 --> 00:47:09,191
you know, doing sepia tones,    
smoothing edges.                

941
00:47:09,260 --> 00:47:11,860
Just about everything you       
could possibly imagine doing    

942
00:47:11,929 --> 00:47:14,329
to manipulate your image,       

943
00:47:14,398 --> 00:47:16,832
this Core Image will do.        
There's also as part of         

944
00:47:16,901 --> 00:47:20,068
the whole machine learning      
stuff that came out in iOS,     

945
00:47:20,137 --> 00:47:24,072
is that, I think it's iOS 11    
or iOS 10, I guess iOS 11.      

946
00:47:24,141 --> 00:47:26,041
There's a whole framework       
called the Vision Framework,    

947
00:47:26,110 --> 00:47:28,744
and Vision can look at          
an image and recognize things   

948
00:47:28,813 --> 00:47:32,314
like faces, bar codes, things   
like that. You can even,        

949
00:47:32,383 --> 00:47:35,451
with machine learning, teach    
it to recognize, you know, is   

950
00:47:35,520 --> 00:47:39,822
that a hat, okay? So [LAUGH]    
you can even do that as well.   

951
00:47:39,890 --> 00:47:41,924
So if you're doing              
sophisticated image stuff,      

952
00:47:41,993 --> 00:47:44,793
again, I don't have time        
to cover any of this but        

953
00:47:44,862 --> 00:47:49,064
just know that it's there.      
All right, so that's it for     

954
00:47:49,133 --> 00:47:51,734
today except for the demo.      
I'm going to do a demo and      

955
00:47:51,803 --> 00:47:53,402
what we're going to do is       
we're going to make it so       

956
00:47:53,470 --> 00:47:56,305
that an emoji art, we can       
set our background image        

957
00:47:56,374 --> 00:47:58,974
with the camera. It's obvious   
thing to want to do instead     

958
00:47:59,043 --> 00:48:02,545
of having to drag and           
drop from another app, and      

959
00:48:02,613 --> 00:48:05,047
our next lecture is our         
last lecture, okay?             

960
00:48:05,116 --> 00:48:08,784
It's on accessibility. And, of  
course, one week from today,    

961
00:48:08,853 --> 00:48:10,519
you're going to have            
your final presentations.       

962
00:48:10,587 --> 00:48:14,990
Be ready to go on that. We're   
about halfway through your      

963
00:48:15,059 --> 00:48:19,628
final projects. Hopefully       
you're halfway done? I hope,    

964
00:48:19,697 --> 00:48:23,799
anyway. So, that's about it.    
So let's dive right into        

965
00:48:23,867 --> 00:48:28,336
the demo, unless there's any    
questions about that? Okay,     

966
00:48:28,405 --> 00:48:33,942
let's get rid of that and lets  
get rid of playing card here.   

967
00:48:34,011 --> 00:48:36,879
And here we are with emoji      
art. All right, so hopefully    

968
00:48:36,948 --> 00:48:39,248
all of you remember emoji       
art from the last lecture,      

969
00:48:39,317 --> 00:48:41,050
the last lecture was            
a quite a while ago,            

970
00:48:41,118 --> 00:48:43,185
from Thanksgiving,              
but here we are.                

971
00:48:43,254 --> 00:48:45,587
Remember last time we did       
all these various segues and    

972
00:48:45,656 --> 00:48:48,523
stuff. But, what I'm gonna do,  
in terms of UI for              

973
00:48:48,592 --> 00:48:51,961
this camera thing is, I'm just  
gonna add a button right here,  

974
00:48:52,029 --> 00:48:55,130
okay, which is going to         
bring up the camera.            

975
00:48:55,199 --> 00:48:57,733
And then, when you take         
a picture, it's gonna use that  

976
00:48:57,802 --> 00:48:59,668
picture as the background,      
couldn't be simpler.            

977
00:48:59,737 --> 00:49:03,939
So, let's go add that button,   
and go down here, and say, bar  

978
00:49:04,007 --> 00:49:08,677
button item, of course. Drag    
it out here. I believe yes,     

979
00:49:08,746 --> 00:49:13,182
there is a system one here for  
a camera. There it is,          

980
00:49:13,251 --> 00:49:16,052
looks just like a camera. Now,  
I'm going to connect this up    

981
00:49:16,120 --> 00:49:19,888
to my code both with            
an action and with an outlet.   

982
00:49:19,957 --> 00:49:21,957
And the reason I'm              
going to do that,               

983
00:49:22,026 --> 00:49:24,259
is I'm going to check to see    
if my device has a camera, and  

984
00:49:24,328 --> 00:49:27,629
if it doesn't, I'm going to     
disable this button. Okay? And  

985
00:49:27,698 --> 00:49:29,731
I told you, you always have     
to check for the device,        

986
00:49:29,800 --> 00:49:33,636
and that's how I'm going        
to check. So let's do that,     

987
00:49:33,704 --> 00:49:36,638
let's go over here.             
Nice and wide,                  

988
00:49:36,707 --> 00:49:41,510
let's put all our camera        
stuff at the top. Mark          

989
00:49:41,579 --> 00:49:45,647
camera. Alright, so             
let's go over here,             

990
00:49:45,716 --> 00:49:50,285
I'm just going to control       
drag. Do the outlet first.      

991
00:49:50,354 --> 00:49:55,457
We'll call this my              
camera button. And then,        

992
00:49:55,526 --> 00:50:01,630
let's do our action.            
And of course, it's             

993
00:50:01,699 --> 00:50:04,233
gonna be BarButtonItem type.    
And we're gonna call this,      

994
00:50:04,302 --> 00:50:07,669
how about we'll call this take  
background photo, cuz that's    

995
00:50:07,738 --> 00:50:10,839
what this button does it takes  
the photo and this is going to  

996
00:50:10,908 --> 00:50:15,177
be the background. All right,   
that's it for our UI,           

997
00:50:15,246 --> 00:50:18,146
we don't have to do anything    
more there, so let's implement  

998
00:50:18,215 --> 00:50:21,083
this stuff, let's start right   
off with the camera button.     

999
00:50:21,152 --> 00:50:24,553
I'm going to write when its     
set, I'm going to enable it or  

1000
00:50:24,622 --> 00:50:26,755
disable it depending on         
whether I have a camera.        

1001
00:50:26,824 --> 00:50:31,927
So I'm just gonna say that      
my camera Button.isEnabled      

1002
00:50:31,995 --> 00:50:35,431
equals my                       
UIImagePickerController         

1003
00:50:35,499 --> 00:50:40,369
.isSourceTypeAvailable.camera   
okay? Here is why I             

1004
00:50:40,437 --> 00:50:44,806
told you gotta test it I'm      
testing it right here okay? So  

1005
00:50:44,875 --> 00:50:48,877
these are not gonna be able to  
get into this code down here    

1006
00:50:48,945 --> 00:50:52,681
if we don't have a camera.      
All right, take a photo really  

1007
00:50:52,750 --> 00:50:57,085
easy, we just create a picker   
UImagePickerController.         

1008
00:50:57,154 --> 00:51:01,623
We're gonna configure it to     
have the right sourceType.      

1009
00:51:01,692 --> 00:51:04,693
We want the camera. Now again,  
we could do photo library and   

1010
00:51:04,761 --> 00:51:06,762
stuff here, if we did           
Photo Library though,           

1011
00:51:06,831 --> 00:51:09,064
that little camera button       
would be bring up or            

1012
00:51:09,133 --> 00:51:11,700
pop over. Okay, but here we're  
gonna do camera, so it's gonna  

1013
00:51:11,769 --> 00:51:15,504
be full screen presentation.    
We want an image here, so       

1014
00:51:15,573 --> 00:51:19,708
I'm gonna say the mediaTypes    
equals an array that has        

1015
00:51:19,776 --> 00:51:25,814
kUTTypeImage, okay.             
And this is not turning purple  

1016
00:51:25,882 --> 00:51:28,150
because it's not recognized     
cuz I have to go up here and    

1017
00:51:28,218 --> 00:51:31,553
say import MobileCoreServices,  
only just to get that one       

1018
00:51:31,622 --> 00:51:33,889
symbol. That's the only         
reason I had to do that. And    

1019
00:51:33,957 --> 00:51:36,191
now it's complaining            
that it's a CFString. So        

1020
00:51:36,260 --> 00:51:41,230
I'm gonna say as string, okay?  
So that's the types I want.     

1021
00:51:41,299 --> 00:51:42,731
I just want images,             
I don't want video.             

1022
00:51:42,800 --> 00:51:47,335
Just want images in this case.  
And sure, we'll allow editing,  

1023
00:51:47,404 --> 00:51:51,240
allows editing, true, why not?  
Most importantly,               

1024
00:51:51,309 --> 00:51:53,108
we gotta set the delegate       
to ourself or                   

1025
00:51:53,177 --> 00:51:56,078
we'll never find out about      
anything the camera did and     

1026
00:51:56,147 --> 00:52:00,615
then we can just present        
this picker animated true of    

1027
00:52:00,684 --> 00:52:04,386
course. Now we are getting an   
error here of course because    

1028
00:52:04,454 --> 00:52:07,856
we are say delegating=self but  
we don't say that we            

1029
00:52:07,925 --> 00:52:10,826
are a UIImagePicker             
ControllerDelegate.             

1030
00:52:10,895 --> 00:52:13,795
And you'd think that            
would be enough to,             

1031
00:52:13,864 --> 00:52:17,532
when we compile get rid of      
the error but it says cannot    

1032
00:52:17,601 --> 00:52:21,536
assign value to UIImagePicker   
ControllerDelegate and          

1033
00:52:21,605 --> 00:52:25,040
UINavigation                    
ControllerDelegate what?        

1034
00:52:25,108 --> 00:52:26,242
Why is it saying that?          

1035
00:52:26,310 --> 00:52:29,111
Well unfortunately the          
UIPickerController I believe    

1036
00:52:29,179 --> 00:52:31,980
it's a subclass of              
UINavigationController so       

1037
00:52:32,049 --> 00:52:35,016
you have to,                    
be its delegate as well.        

1038
00:52:35,085 --> 00:52:36,785
So we just have to              
say UINavigate, and             

1039
00:52:36,853 --> 00:52:39,321
this is the case by the way     
where the fix it down here,     

1040
00:52:39,389 --> 00:52:43,358
you do not want this fix it,    
this fix it is to cast self,    

1041
00:52:43,427 --> 00:52:45,527
to be these things,             
which it£s not. So              

1042
00:52:45,595 --> 00:52:48,129
be carefull of fix its, it£s    
always the right thing. So      

1043
00:52:48,198 --> 00:52:51,400
here I£m gonna be UINavigation  
ControllerDelegate as well.     

1044
00:52:51,469 --> 00:52:54,169
Luckily, neither of these       
have any required methods,      

1045
00:52:54,238 --> 00:52:56,004
although, in                    
UIImagePickerController,        

1046
00:52:56,073 --> 00:52:57,139
they should be required.        

1047
00:52:57,207 --> 00:53:00,876
Because, you can£t really do    
anything without them. And      

1048
00:53:00,944 --> 00:53:02,678
let's jump right to             
those delegate methods.         

1049
00:53:02,746 --> 00:53:05,480
There's only two of them.       
So image picker. There's this   

1050
00:53:05,549 --> 00:53:09,985
one, which is cancel. And then  
there's this one, other one,    

1051
00:53:10,053 --> 00:53:13,055
imagePickerController.          
Which is the didFinish          

1052
00:53:13,123 --> 00:53:16,959
PickingMediaWithInfo. And       
in both of them, I'm gonna say  

1053
00:53:17,028 --> 00:53:22,197
the picker.presenting           
ViewController dismiss,         

1054
00:53:22,266 --> 00:53:26,968
okay anyone it's time to        
go animated true. Now,          

1055
00:53:27,037 --> 00:53:32,874
who is the pickers presenting   
the view controller? It's us.   

1056
00:53:32,943 --> 00:53:36,144
Cuz we're presenting it. So,    
I could actually just get rid   

1057
00:53:36,213 --> 00:53:39,181
of this right?                  
This would actually be okay.    

1058
00:53:39,249 --> 00:53:42,117
But I kinda like to do          
this explicitly. Just,          

1059
00:53:42,185 --> 00:53:45,553
I don't know, for some reason   
it just, you know, because      

1060
00:53:45,622 --> 00:53:47,923
that dismiss has that weird     
thing where it'll look and      

1061
00:53:47,992 --> 00:53:51,125
see if you're presented by,     
a person and... I like to have  

1062
00:53:51,194 --> 00:53:53,695
it explicit to be the pickers   
presenting the viewController.  

1063
00:53:53,763 --> 00:53:56,932
What if I put up another view   
controller that presented       

1064
00:53:57,000 --> 00:53:59,435
the pet camera and then it      
was unwinding back to here or   

1065
00:53:59,503 --> 00:54:02,104
something like that. I don't    
know, so. I like to do that,    

1066
00:54:02,173 --> 00:54:06,474
and I wanna do this in          
both places, both when,         

1067
00:54:06,543 --> 00:54:07,976
if it's canceled or             

1068
00:54:08,045 --> 00:54:11,347
whether it successfully         
picks some media here.          

1069
00:54:12,749 --> 00:54:16,852
All right, so now we have this  
ImagePickerController and       

1070
00:54:16,921 --> 00:54:21,657
it successfully picks some,     
some image or whatever that we  

1071
00:54:21,725 --> 00:54:23,792
want to use. How do we get      
that image out of there?        

1072
00:54:23,861 --> 00:54:25,995
Well it comes out of this       
dictionary right here.          

1073
00:54:26,063 --> 00:54:27,629
So we're going to look          
in that dictionary and          

1074
00:54:27,697 --> 00:54:30,899
say if I can let the image      
equal that info dictionary and  

1075
00:54:30,968 --> 00:54:34,837
I'm going to look at the key    
UIImagePickerController.        

1076
00:54:36,040 --> 00:54:40,142
Edited image. Okay?             
I allow editing, so             

1077
00:54:40,210 --> 00:54:42,944
I'm going to do this.           
Now, notice that the type in    

1078
00:54:43,013 --> 00:54:45,647
the dictionary is any because   
that might be UI image,         

1079
00:54:45,716 --> 00:54:49,184
it might be URL, okay? It       
could be a PH live photo, so    

1080
00:54:49,253 --> 00:54:53,721
it's any- so we are required    
here to say as a UIImage.       

1081
00:54:53,790 --> 00:54:56,792
Okay. So this gets the image.   
Now, I'm going to do two other  

1082
00:54:56,860 --> 00:54:59,994
small things here. One is,      
I'm gonna actually say if this  

1083
00:55:00,063 --> 00:55:03,665
is nill, because maybe I went   
back and changed this to false  

1084
00:55:03,734 --> 00:55:08,369
in the future, then I'm going   
to also back up by grabbing     

1085
00:55:08,438 --> 00:55:14,843
the UIImagePicker               
OriginalImage,                  

1086
00:55:14,911 --> 00:55:18,846
okay? So basically I'm just,    
if I ever change this,          

1087
00:55:18,915 --> 00:55:21,650
I want the rest of the code to  
still work. So I'm just kinda,  

1088
00:55:21,718 --> 00:55:24,386
if this is nil then I'm         
gonna grab this one             

1089
00:55:24,454 --> 00:55:27,689
instead. The other thing I      
wanna do here is shrinks this   

1090
00:55:27,758 --> 00:55:30,725
image down a little bit.        
Because, some of these cameras  

1091
00:55:30,794 --> 00:55:34,429
are huge. I£m, this image       
would be four megabytes in      

1092
00:55:34,498 --> 00:55:37,799
size. And in emoji art,         
you know, usually they don£t    

1093
00:55:37,868 --> 00:55:40,702
want the emojis to be these     
tiny little dots in a gigantic  

1094
00:55:40,771 --> 00:55:44,072
image, right? So                
meaning the emoji only has so   

1095
00:55:44,141 --> 00:55:47,042
much resolution.                
So I'm gonna shrink this down.  

1096
00:55:47,111 --> 00:55:50,078
And I'm gonna do that with a    
little function that I have in  

1097
00:55:50,147 --> 00:55:54,182
my utilities called scaled by.  

1098
00:55:54,251 --> 00:55:57,619
And scaled by is the world's    
cheapest little image scaler.   

1099
00:55:57,687 --> 00:56:00,922
It actually scales it, not      
even by the area of the image,  

1100
00:56:00,991 --> 00:56:03,325
but it scales                   
the edges by that much          

1101
00:56:03,393 --> 00:56:04,826
which is kinda                  
freaky way to do it.            

1102
00:56:04,895 --> 00:56:07,462
But it's simple code and        
you can go look at it,          

1103
00:56:07,531 --> 00:56:12,367
it's in the utilities .swift    
that I provide with EmojiArt.   

1104
00:56:12,435 --> 00:56:14,603
Okay, so now I've got           
the image I want, hopefully,    

1105
00:56:14,672 --> 00:56:17,439
right? if let, so               
hopefully, I got the image.     

1106
00:56:17,508 --> 00:56:21,609
Now I need to set this as my    
EmojiArt's background, right?   

1107
00:56:21,678 --> 00:56:24,346
Well, because we wrote          
our code so nicely,             

1108
00:56:24,415 --> 00:56:27,348
we can just say,                
emojiArtBackgroundImage =.      

1109
00:56:27,417 --> 00:56:29,150
Now I wanna say image, but      

1110
00:56:29,219 --> 00:56:33,055
do you remember what this       
argument is? It's a tuple,      

1111
00:56:33,123 --> 00:56:37,659
remember that, we changed       
[LAUGH] that to a tuple?        

1112
00:56:37,727 --> 00:56:40,962
What am I gonna put as          
the URL here? Because I got     

1113
00:56:41,031 --> 00:56:44,332
that image directly from the    
camera and I don't have a URL.  

1114
00:56:44,401 --> 00:56:47,468
So I'm gonna have to, for now   
anyway, and if I have time,     

1115
00:56:47,537 --> 00:56:50,405
I'll show you a better way I'm  
gonna have to create a URL for  

1116
00:56:50,474 --> 00:56:51,339
this thing, okay?               

1117
00:56:51,408 --> 00:56:54,976
And I'm gonna create a URL in   
my sandbox, okay, that stores   

1118
00:56:55,045 --> 00:56:57,278
this image. I actually have     
a little utility function       

1119
00:56:57,347 --> 00:57:00,348
to do that as well. You can go  
look at that in the code. So    

1120
00:57:00,417 --> 00:57:03,218
I'm gonna say so                
I'm gonna create that.          

1121
00:57:03,286 --> 00:57:05,254
Also, and the other thing       
we wanna do, by the way,        

1122
00:57:05,322 --> 00:57:07,489
is note that our document       
has changed here, right?        

1123
00:57:07,558 --> 00:57:10,291
If we set our background        
image, then our document        

1124
00:57:10,360 --> 00:57:14,029
has definitely changed. So I'm  
going to create this little     

1125
00:57:14,097 --> 00:57:18,800
URL, let url =, take my image,  
and I, the function I have      

1126
00:57:18,869 --> 00:57:23,171
is called storeLocallyAsJPEG    
with a name.                    

1127
00:57:23,240 --> 00:57:26,041
So that's what this does.       
It store, takes a UIImage,      

1128
00:57:26,109 --> 00:57:29,010
all right, this is a UIImage    
extension method, and           

1129
00:57:29,079 --> 00:57:31,613
it stores it as a name.         
Now, I need a unique name for   

1130
00:57:31,682 --> 00:57:34,950
this thing. A really great      
unique name is the current      

1131
00:57:35,019 --> 00:57:37,919
date as seconds since           
January 1st, 1970, okay?        

1132
00:57:37,987 --> 00:57:40,956
Turns out the easy              
way to get that,                

1133
00:57:41,025 --> 00:57:46,528
which is Date.timeInterval      
SinceReferenceDate, okay?       

1134
00:57:46,597 --> 00:57:49,497
Of course, this is going to be  
seconds so that's a double.     

1135
00:57:49,566 --> 00:57:53,635
So I'm going to turn it into a  
string by just stringifying it  

1136
00:57:53,704 --> 00:57:57,506
here. And now I have            
a nice unique name for          

1137
00:57:57,575 --> 00:58:01,843
this JPEG. Now, I hate          
this because I just took        

1138
00:58:01,911 --> 00:58:04,946
a picture with the camera and   
I'm having to create this       

1139
00:58:05,015 --> 00:58:06,848
random file in my file system.  

1140
00:58:06,916 --> 00:58:10,251
When am I gonna clean this      
thing up? Okay, I'm gonna have  

1141
00:58:10,320 --> 00:58:13,254
to find out when my document    
was deleted somehow or and      

1142
00:58:13,323 --> 00:58:16,191
what about on iCloud? This      
is not gonna work on iCloud.    

1143
00:58:16,259 --> 00:58:18,794
If I open this on another       
device, it can't see my         

1144
00:58:18,862 --> 00:58:21,863
sandbox on this other device.   
So this is terrible, okay?      

1145
00:58:21,931 --> 00:58:24,766
Now, we're gonna be close on    
time here so I don't know if    

1146
00:58:24,835 --> 00:58:27,301
I'm gonna be able to            
show you how to fix this.       

1147
00:58:27,370 --> 00:58:29,971
But I don't like this, but      
we're gonna do this just so     

1148
00:58:30,040 --> 00:58:31,806
that we can see                 
this all working so             

1149
00:58:31,875 --> 00:58:34,342
you can see the Camera API      
working, etc., okay?            

1150
00:58:34,411 --> 00:58:35,177
So let's do that.               

1151
00:58:35,245 --> 00:58:39,281
Let's take a look at this.      
Let's go to our iPad here. So   

1152
00:58:39,349 --> 00:58:42,184
here's EmojiArt, let's          
create a new document here.     

1153
00:58:42,252 --> 00:58:45,019
I just created, I pressed       
Create New Document. And        

1154
00:58:45,088 --> 00:58:47,755
you can see we got our camera   
up there in the upper right.    

1155
00:58:47,824 --> 00:58:50,292
And notice that it's also       
enabled, that's good.           

1156
00:58:50,361 --> 00:58:52,194
That means we have a camera     
on this device. So              

1157
00:58:52,262 --> 00:58:55,497
I'm gonna click that camera.    
Okay,                           

1158
00:58:55,565 --> 00:58:58,933
it's gonna load up the camera,  
bring up this, here it is.      

1159
00:58:59,002 --> 00:59:02,404
We're gonna do a blast from     
the past right here and         

1160
00:59:02,473 --> 00:59:06,274
go picture our picture          
from our concentration.         

1161
00:59:06,343 --> 00:59:08,076
This is kind of                 
nostalgia day here,             

1162
00:59:08,144 --> 00:59:10,445
kinda going back to playing     
card in this. So here,          

1163
00:59:10,514 --> 00:59:13,148
let's try and take a picture    
without that shadow in there.   

1164
00:59:13,216 --> 00:59:15,183
There we go. And here's         
what I was talking about,       

1165
00:59:15,252 --> 00:59:17,085
where I can zoom in on this,    
or                              

1166
00:59:17,154 --> 00:59:20,622
change the cropping rectangle   
cuz we allow editing. So        

1167
00:59:20,691 --> 00:59:22,056
we'll do that. And              
I'm gonna hit Use Photo and     

1168
00:59:22,125 --> 00:59:23,358
we're gonna see if              
this is gonna work.             

1169
00:59:23,427 --> 00:59:28,797
And it doesn't work.            
Now, why this doesn't work?     

1170
00:59:28,866 --> 00:59:30,865
You're like, no,                
now I've gotta go debug this.   

1171
00:59:30,934 --> 00:59:32,233
This couldn't                   
possibly not work.              

1172
00:59:32,302 --> 00:59:34,403
This is one of those cases      
where you look at our code.     

1173
00:59:34,471 --> 00:59:37,105
It's so simple here,            
it couldn't work well actually  

1174
00:59:37,173 --> 00:59:39,841
this doesn't work, believe it   
or not because of the view      

1175
00:59:39,910 --> 00:59:43,978
controller life cycle. When we  
press that camera button and    

1176
00:59:44,047 --> 00:59:47,515
bring up the camera             
it actually covers up           

1177
00:59:47,584 --> 00:59:50,652
our view controller entirely.   
And then when it goes away,     

1178
00:59:50,720 --> 00:59:54,923
"view will appear" gets called  
on our view controller. Do      

1179
00:59:54,991 --> 00:59:57,559
you see why? Because it just    
appeared. It was covered up     

1180
00:59:57,627 --> 00:59:59,494
and the camera went away and    
now it appeared.                

1181
00:59:59,562 --> 01:00:01,663
Well let's a look at our        
viewWillAppear down here.       

1182
01:00:02,799 --> 01:00:05,400
Here's our viewWillAppear.      
What do we do in                

1183
01:00:05,468 --> 01:00:09,904
viewWillAppear?                 
We open our document, okay?     

1184
01:00:09,973 --> 01:00:13,274
And we open it no matter what.  
So if it's already open,        

1185
01:00:13,343 --> 01:00:16,010
we open it again. We go back    
to disk and get it again.       

1186
01:00:16,079 --> 01:00:18,580
That's what's happening here,   
it actually was working. It     

1187
01:00:18,649 --> 01:00:21,115
put that image in there, but    
then it reopened the document   

1188
01:00:21,184 --> 01:00:24,385
and went back to blank, cuz it  
was an untitled document. So    

1189
01:00:24,454 --> 01:00:28,155
this is a simple fix here.      
We're just gonna say,           

1190
01:00:28,224 --> 01:00:33,662
if our document state is not,   
Normal.                         

1191
01:00:33,731 --> 01:00:40,902
Then, we'll open our            
document here. Okay?            

1192
01:00:40,970 --> 01:00:43,705
But that's kind of a tricky     
bug, when I went to prepare,    

1193
01:00:43,773 --> 01:00:47,341
add this before class. I was    
like why doesn't that work?     

1194
01:00:47,410 --> 01:00:50,311
And so this is a little bit     
of a tricky one there, but      

1195
01:00:50,380 --> 01:00:52,046
this will fix it.               
So let's go back up there and   

1196
01:00:52,115 --> 01:00:56,017
get this code on screen for     
our camera here and             

1197
01:00:56,086 --> 01:01:00,889
run again. To bring our         
untitled document up again,     

1198
01:01:00,958 --> 01:01:05,560
oops. That one screen so        
you can see it.                 

1199
01:01:05,629 --> 01:01:06,994
All right, so                   
gather untitled documents.      

1200
01:01:07,063 --> 01:01:10,164
So I'm gonna hit the camera     
button again. Go up here,       

1201
01:01:10,233 --> 01:01:14,736
let's take a photo and          
get in focus right there.       

1202
01:01:16,306 --> 01:01:20,275
Cute little guy there, okay?    
So this now I'm gonna say       

1203
01:01:20,343 --> 01:01:23,245
use photo and sure enough,      
here it is, okay?               

1204
01:01:23,313 --> 01:01:27,448
Here's our photo and            
we can add apples or whatever,  

1205
01:01:27,517 --> 01:01:31,119
maybe like a bee caught in the  
web up there, make sense. And   

1206
01:01:31,187 --> 01:01:33,588
we're done. Hopefully we'll     
get a thumbnail there.          

1207
01:01:33,657 --> 01:01:39,293
We even get a thumbnail,        
that's great. Okay. Now,        

1208
01:01:39,362 --> 01:01:42,130
let's talk a little bit about   
what I was talking about where  

1209
01:01:42,199 --> 01:01:44,866
this is bad because it creates  

1210
01:01:46,469 --> 01:01:50,838
a little local file for this.   
How are we gonna fix that?      

1211
01:01:50,907 --> 01:01:53,074
Well I'm gonna fix that at      
light speed here because we     

1212
01:01:53,142 --> 01:01:54,676
have ten minutes left.          

1213
01:01:54,744 --> 01:01:57,045
The way I'm gonna do it is      
I'm actually gonna store        

1214
01:01:57,113 --> 01:02:01,115
the camera's image in my        
emoji art document, okay.       

1215
01:02:01,184 --> 01:02:03,484
So I'm not gonna store it       
as a URL, a separate thing.     

1216
01:02:03,553 --> 01:02:06,288
I'm actually gonna store the    
data embedded in my document.   

1217
01:02:07,724 --> 01:02:09,590
Okay, that way it'll work in    
icloud and all the stuff and    

1218
01:02:09,659 --> 01:02:11,726
I won't have to create the URL  
it's going to be great.         

1219
01:02:11,795 --> 01:02:14,929
Now I'm not gonna do that for   
documents that do have a URL    

1220
01:02:14,998 --> 01:02:16,898
because I don't want my         
to duplicate that image,        

1221
01:02:16,967 --> 01:02:18,766
no need to do that we just      
go out on the internet and      

1222
01:02:18,835 --> 01:02:21,936
get it. But for cases where I   
don't have the URL I'm going    

1223
01:02:22,005 --> 01:02:25,306
to do that. So let's again at   
light speed I'm going to limit  

1224
01:02:25,375 --> 01:02:28,909
the explanation here because    
time constraint but I'll.       

1225
01:02:28,978 --> 01:02:32,113
I think you'll learn something  
from doing it, let's go do it.  

1226
01:02:32,182 --> 01:02:35,049
Now the first thing I           
need to do is go back to        

1227
01:02:35,118 --> 01:02:39,186
my EmojiArt model and make it   
capable of having the image,    

1228
01:02:39,255 --> 01:02:41,823
cuz right now it has            
to have a URL. So               

1229
01:02:41,892 --> 01:02:44,225
I'm gonna make having           
URL be optional and             

1230
01:02:44,294 --> 01:02:47,094
have a new one called           
ImageData which is just a data  

1231
01:02:47,163 --> 01:02:49,864
object. Notice this is not      
a UI image cuz this is          

1232
01:02:49,933 --> 01:02:53,934
not a UI thing because this is  
my model. And since I can now   

1233
01:02:54,003 --> 01:02:58,373
have either URL or image data   
I'm gonna go down to here and   

1234
01:02:58,442 --> 01:03:00,241
have a different                
initializer or                  

1235
01:03:00,310 --> 01:03:03,478
another initializer actually    
that let's me initialize        

1236
01:03:04,648 --> 01:03:09,918
an image data based.            
Oops, not image data,           

1237
01:03:09,986 --> 01:03:14,355
data. This is imageData         
= imageData. Okay so            

1238
01:03:14,424 --> 01:03:19,794
now I can create my emoji art   
with either URL or image data.  

1239
01:03:19,863 --> 01:03:23,231
Now, what about Codeable, what  
about turning this to .json,    

1240
01:03:23,300 --> 01:03:27,001
is this all just going to       
work? Well yeah, no errors      

1241
01:03:27,070 --> 01:03:30,037
right? And in fact it is gonna  
work because Codeable knows     

1242
01:03:30,106 --> 01:03:33,141
how to deal with optionals, it  
knows how to write out datas,   

1243
01:03:33,210 --> 01:03:36,210
so this is all perfectly fine,  
it's all just gonna work. So    

1244
01:03:36,279 --> 01:03:38,880
that was easy, let's go back.   
To our emoji art view           

1245
01:03:38,949 --> 01:03:41,249
controller. Now what's          
the problem here? Well,         

1246
01:03:41,318 --> 01:03:45,787
the real problem over here is   
this method right down here.    

1247
01:03:45,856 --> 01:03:49,390
Okay, this is the core of the   
problem, right here [LAUGH]     

1248
01:03:49,459 --> 01:03:52,026
okay? This is our               
emojiArtBackgroundImage,        

1249
01:03:52,095 --> 01:03:54,462
which is that tuple.            
Remember the tuple we had?      

1250
01:03:54,531 --> 01:03:56,897
Okay, well, that tuple          
has a URL in the image.         

1251
01:03:56,966 --> 01:04:01,335
But now it might be image       
data in the image. Okay, so     

1252
01:04:01,404 --> 01:04:04,205
we have to fix this. This       
can no longer be this tuple.    

1253
01:04:04,274 --> 01:04:07,976
It has to be some other         
type that's either a URL or     

1254
01:04:08,044 --> 01:04:10,578
it's the image data. Now what   
kind of data structure we       

1255
01:04:10,646 --> 01:04:14,015
use when something is either    
one thing or another?           

1256
01:04:14,084 --> 01:04:18,986
What do we use? What?           
>> [INAUDIBLE]                  

1257
01:04:19,055 --> 01:04:20,288
>> Any, we could use any, but   

1258
01:04:20,356 --> 01:04:22,690
that's not very Swifty.         
>> A enum?                      

1259
01:04:22,759 --> 01:04:24,525
>> enum, absolutely.            

1260
01:04:24,594 --> 01:04:25,693
Let's use an enum here.         

1261
01:04:25,762 --> 01:04:27,595
I'm gonna say                   
enum ImageSource,               

1262
01:04:27,664 --> 01:04:28,696
I'm gonna call it.              

1263
01:04:28,765 --> 01:04:32,367
And it's gonna have the remote  
case which has a URL and        

1264
01:04:32,435 --> 01:04:38,172
the UIImage. Okay, and it's     
going to have the local case    

1265
01:04:38,241 --> 01:04:42,576
where it's an image data and a  
UIImage. Now for convenience,   

1266
01:04:42,645 --> 01:04:45,180
I'm gonna create a var.         
Notice they both have UIImage.  

1267
01:04:45,248 --> 01:04:47,081
So I'm gonna create             
a var called image here,        

1268
01:04:47,150 --> 01:04:48,549
which returns to that UIImage.  

1269
01:04:48,618 --> 01:04:52,419
And I'm just gonna do that      
by switching on myself. And     

1270
01:04:52,488 --> 01:04:56,724
in the case of a remote, then   
I don't care what the URL is.   

1271
01:04:56,793 --> 01:05:00,328
But I'm gonna get the image     
back here and return it.        

1272
01:05:00,397 --> 01:05:02,997
Okay, and in the case of        
local, I don't care what        

1273
01:05:03,066 --> 01:05:06,534
the data is. I'm just gonna     
get the image and return that   

1274
01:05:06,603 --> 01:05:09,537
image, okay? So this is just    
a nice little convenience var,  

1275
01:05:09,605 --> 01:05:12,006
so I can get the image,         
no matter which one it is.      

1276
01:05:12,075 --> 01:05:15,042
All right, so                   
now I'm gonna change this.      

1277
01:05:15,111 --> 01:05:17,945
I'm gonna change this tuple     
to be an ImageSource which      

1278
01:05:18,014 --> 01:05:21,048
has to be optional because we   
might have a blank document.    

1279
01:05:21,117 --> 01:05:23,484
It has no background. So we'll  
have to leave it optional. And  

1280
01:05:23,553 --> 01:05:26,487
I'm not gonna have it be        
a computed var anymore.         

1281
01:05:26,556 --> 01:05:29,357
I'm gonna have it be stored.    
And I'm gonna use didSet to do  

1282
01:05:29,426 --> 01:05:32,861
all this stuff down here. And   
I don't have to keep the URL    

1283
01:05:32,929 --> 01:05:35,863
separately anymore, cuz it's    
built into the ImageSource.     

1284
01:05:35,932 --> 01:05:37,899
And everywhere where            
I did newValue,                 

1285
01:05:37,968 --> 01:05:40,468
well in the computed sense,     
is now this thing,              

1286
01:05:40,536 --> 01:05:44,272
okay? Which, is optional, so    
it might be optional there.     

1287
01:05:44,341 --> 01:05:48,275
So this is also optional. And,  
the image, which is this var    

1288
01:05:48,344 --> 01:05:50,612
I just created right there,     
is not optional, so             

1289
01:05:50,680 --> 01:05:53,648
we'll take that away. So this   
is great! I just fixed it!      

1290
01:05:53,716 --> 01:05:55,950
Okay, the moment you            
heard background image.         

1291
01:05:56,019 --> 01:05:58,786
Now of course we need to go     
all the places we set and       

1292
01:05:58,854 --> 01:06:02,857
get this, okay, to fix it to    
work. Well, let's start with    

1293
01:06:02,926 --> 01:06:05,493
our camera, where we set the    
camera. That's right up here.   

1294
01:06:05,562 --> 01:06:08,963
This is the code right here     
where we say url image. Well,   

1295
01:06:09,032 --> 01:06:12,233
I don't wanna do url anymore    
so I'm gonna get rid of that.   

1296
01:06:12,302 --> 01:06:15,437
So that clearly makes this be   
the local case where I'm gonna  

1297
01:06:15,505 --> 01:06:18,539
have imageData and the image    
that was passed in. So          

1298
01:06:18,608 --> 01:06:21,276
where do I get the imageData?   
Well, we know how to do that.   

1299
01:06:21,344 --> 01:06:22,309
I'm gonna say if                

1300
01:06:22,378 --> 01:06:25,980
I can let the imageData equal   
the UI JPEG thing, this thing   

1301
01:06:26,049 --> 01:06:29,684
right here, UIImageJPEG         
Representation, of the image,   

1302
01:06:29,752 --> 01:06:32,686
will have a lossless            
compression right there.        

1303
01:06:32,755 --> 01:06:37,091
And as long as we are able to   
do that, then we will do this.  

1304
01:06:37,160 --> 01:06:40,561
Otherwise, I probably have      
a to do here to go and          

1305
01:06:40,630 --> 01:06:45,033
put up an alert, alert user of  
bad camera input or something,  

1306
01:06:45,101 --> 01:06:47,902
okay? Cuz I wasn't able to      
turn the thing from the camera  

1307
01:06:47,971 --> 01:06:49,337
into a JPEG, for some reason.   

1308
01:06:49,405 --> 01:06:50,638
I don't know why that           
would ever happen but           

1309
01:06:50,707 --> 01:06:52,806
I should probably put           
up an alert here.               

1310
01:06:52,875 --> 01:06:55,677
Okay, so we fixed that one.     
Where else do we do this?       

1311
01:06:55,746 --> 01:06:58,379
Well, we do it when we drop,    
okay, right?                    

1312
01:06:58,448 --> 01:07:01,082
When we drop an image in,       
drag and drop a background,     

1313
01:07:01,151 --> 01:07:04,351
of course we do it there. Now   
here, look at all this stuff    

1314
01:07:04,420 --> 01:07:07,054
we did last lecture to go       
put up an alert if the thing    

1315
01:07:07,123 --> 01:07:09,657
we dropped in we couldn't       
get the image. Actually, we     

1316
01:07:09,726 --> 01:07:12,193
don't have to do that anymore.  
Because now if someone drags    

1317
01:07:12,262 --> 01:07:16,230
in a bad URL we can use the     
image, use its image data. So   

1318
01:07:16,299 --> 01:07:18,232
I'm actually gonna              
get rid of all of               

1319
01:07:18,301 --> 01:07:21,102
this stuff that we did last     
time. What a waste of time      

1320
01:07:21,171 --> 01:07:24,172
last lecture was. And instead   
I'm gonna go back to exactly    

1321
01:07:24,240 --> 01:07:27,441
what we had before which is     
use the image fetcher. Okay,    

1322
01:07:27,510 --> 01:07:31,279
but what I'm gonna do here is   
well, first we gotta update     

1323
01:07:31,347 --> 01:07:35,283
this, right, to the background  
image in the ImageFetcher       

1324
01:07:35,352 --> 01:07:39,987
world. So this is remote        
with the URL and the image.     

1325
01:07:40,056 --> 01:07:43,791
However, what if we had to      
resort to our backup image?     

1326
01:07:43,860 --> 01:07:46,894
Because then it's not really    
remote. Now it's become local.  

1327
01:07:46,963 --> 01:07:50,398
So I'm going to say             
here if the image was           

1328
01:07:50,467 --> 01:07:53,501
the imageFetcher's              
backup image                    

1329
01:07:53,570 --> 01:07:57,839
then I'm going to do            
one thing, else, oops.          

1330
01:08:00,009 --> 01:08:03,845
Else I'm gonna do another. So   
the else is to do the normal    

1331
01:08:03,913 --> 01:08:06,681
remote case cuz I didn't        
use the backup image. But       

1332
01:08:06,749 --> 01:08:11,219
if I do use the backup image    
here, this becomes local and    

1333
01:08:11,288 --> 01:08:16,357
we have to have the image       
data here, Data. So             

1334
01:08:16,426 --> 01:08:19,327
I need to get the image data    
here too. So I'm going to say   

1335
01:08:19,395 --> 01:08:23,664
if I can let imageData equal    
that UI JPEG thing. There it    

1336
01:08:23,733 --> 01:08:27,869
is. Image compression,          
lossless. Just go in here, and  

1337
01:08:27,938 --> 01:08:31,239
I'm gonna do this.              
What am I'm gonna do if not?    

1338
01:08:31,308 --> 01:08:32,540
If I wasn't doing,              
you want I'm gonna do?          

1339
01:08:32,609 --> 01:08:35,210
I'm going to present            
that warning thing.             

1340
01:08:35,278 --> 01:08:38,779
What was the name of that       
thing? Bad URL warning,         

1341
01:08:38,848 --> 01:08:42,984
bad URL? There it is,           
presentBadURLWarning for        

1342
01:08:43,053 --> 01:08:45,419
that URL. That same alert       
that we were doing before,      

1343
01:08:45,488 --> 01:08:48,356
I'm just gonna present that     
if I wasn't able to take        

1344
01:08:48,424 --> 01:08:50,891
the image that was dragged and  
get it to imageData.            

1345
01:08:50,960 --> 01:08:53,027
Again, I don't know why it      
would ever not be able to.      

1346
01:08:53,095 --> 01:08:55,930
But yeah, let's make our code.  
Okay, good, woohoo.             

1347
01:08:55,998 --> 01:08:59,199
Now every single place where    
we set the background image,    

1348
01:08:59,268 --> 01:09:00,434
both the camera and             

1349
01:09:00,503 --> 01:09:04,238
the other one is now setting    
it to this nice enum here.      

1350
01:09:04,306 --> 01:09:07,108
What about where we use it?     
Okay, well the primary place    

1351
01:09:07,177 --> 01:09:09,744
where we use it is right here   
where all this red is, which    

1352
01:09:09,813 --> 01:09:13,881
is our model, right? Because    
someone sets an emojiArt model  

1353
01:09:13,949 --> 01:09:16,951
and we have to obviously get    
the right data out of there     

1354
01:09:17,020 --> 01:09:20,120
somehow or they're asking for   
it. And we're gonna give it     

1355
01:09:20,189 --> 01:09:22,623
back to them depending on       
the two different cases. So     

1356
01:09:22,692 --> 01:09:25,759
let's do the get case first,    
it's quite simple. Where,       

1357
01:09:25,828 --> 01:09:28,462
instead of looking at the URL   
now I just need to look         

1358
01:09:28,531 --> 01:09:31,766
at this image source thing,     
emojiArtBackgroundImage.        

1359
01:09:31,835 --> 01:09:34,302
Get the image source.           
I still want to do this,        

1360
01:09:34,370 --> 01:09:37,771
which is to get all             
the emojis. But I'm only gonna  

1361
01:09:37,840 --> 01:09:42,010
call this URL one here if this  
imageSource is the remote ca-,  

1362
01:09:42,078 --> 01:09:45,679
case. So I'm gonna switch       
on this imageSource. And        

1363
01:09:45,748 --> 01:09:50,184
if it's the remote case, where  
I'm gonna grab the URL, and     

1364
01:09:50,252 --> 01:09:54,188
I don't care about the image    
in this case, then I'm gonna    

1365
01:09:54,257 --> 01:10:00,761
do this. All right, and         
what if it's the local case,    

1366
01:10:00,830 --> 01:10:04,298
okay, where we got this         
imageData? Well, then I'm just  

1367
01:10:04,367 --> 01:10:08,669
going to return an EmojiArt     
that takes imageData instead.   

1368
01:10:08,738 --> 01:10:14,842
[SOUND] All right, that's it.   
So that was easy.               

1369
01:10:14,911 --> 01:10:18,212
The get case of that was, was   
really easy to do and obvious,  

1370
01:10:18,281 --> 01:10:20,781
what we're doing there.         
What about the set case?        

1371
01:10:20,850 --> 01:10:21,816
Little more complicated.        

1372
01:10:21,885 --> 01:10:24,351
First of all, we don't          
do the tuple (nil, nil).        

1373
01:10:24,420 --> 01:10:27,655
We just say nil cuz it's        
an optional image source right  

1374
01:10:27,723 --> 01:10:30,424
there. Still wanna do this.     
Still wanna check and           

1375
01:10:30,493 --> 01:10:33,294
see if there's a URL and        
try to go fetch it if we can.   

1376
01:10:33,362 --> 01:10:37,164
And if we can successfully      
fetch it, then we do wanna do   

1377
01:10:37,233 --> 01:10:41,368
remote url kinda image          
just like we did before.        

1378
01:10:41,437 --> 01:10:43,136
Now, I'm gonna do the same      
thing here that I did           

1379
01:10:43,205 --> 01:10:46,541
with drop, which is I'm gonna   
use any image data I can find   

1380
01:10:46,609 --> 01:10:49,076
in the emoji art that you're    
setting on me and use it as     

1381
01:10:49,144 --> 01:10:53,748
the backup image. Okay, so      
let's take this down here and   

1382
01:10:53,816 --> 01:11:01,021
say, imageFetch.backup = the    
image that's in the EmojiArt    

1383
01:11:01,090 --> 01:11:03,758
that you're passing me, so I    
better create a var for that.   

1384
01:11:03,826 --> 01:11:08,829
So I'll get the imageData       
out of the newValue. And        

1385
01:11:08,898 --> 01:11:12,900
then I'll get the oops, I'll    
get the image by saying well,   

1386
01:11:12,969 --> 01:11:15,670
if the imageData is             
not nil then I'm gonna          

1387
01:11:15,738 --> 01:11:21,341
return a UIImage from           
that data. Otherwise,           

1388
01:11:21,410 --> 01:11:24,244
I'll just return nil. In other  
words, there is no image data   

1389
01:11:24,313 --> 01:11:26,914
in that EmojiArt so I can't     
use it as a backup. Okay,       

1390
01:11:26,982 --> 01:11:29,016
in that case I'm not going      
to be able to load this,        

1391
01:11:29,085 --> 01:11:31,619
which is fine. That's no        
different than it was before.   

1392
01:11:31,688 --> 01:11:34,288
All right, so there's           
our imageFetcher backup.        

1393
01:11:34,357 --> 01:11:36,357
So now we'll just               
say imageFetcher,               

1394
01:11:36,426 --> 01:11:40,961
fetch that URL. Now,            
when that comes back, okay?     

1395
01:11:41,030 --> 01:11:43,631
We have to use the same exact   
thing we did down with drop,    

1396
01:11:43,699 --> 01:11:46,300
is check and see if we          
used the backup image.          

1397
01:11:46,369 --> 01:11:47,568
Cuz if we used                  
the backup image,               

1398
01:11:47,637 --> 01:11:51,071
we're in the local case.        
So again, I'm gonna say, if     

1399
01:11:51,140 --> 01:11:56,010
the image that we used equals   
our imagefetcher.backup, then,  

1400
01:12:01,484 --> 01:12:06,220
I'm gonna use the local         
case with imageData,            

1401
01:12:06,289 --> 01:12:09,057
right? This is the image        
data from up here               

1402
01:12:10,526 --> 01:12:13,895
which we know this is going to  
not be nil because we wouldn't  

1403
01:12:13,963 --> 01:12:16,697
have gotten this to be not      
nil if this weren't nil.        

1404
01:12:16,766 --> 01:12:19,834
So fine, now what if the thing  
has no URL, URL at all?         

1405
01:12:19,903 --> 01:12:22,636
What if we have an emoji        
art and it has no URL?          

1406
01:12:22,705 --> 01:12:24,404
It's just image data only, so   

1407
01:12:24,473 --> 01:12:27,675
we'd better handle that case    
as well. So here I'm gonna      

1408
01:12:27,744 --> 01:12:30,978
say, where's the other side     
of that if, here it is.         

1409
01:12:31,047 --> 01:12:33,747
I'm gonna say, else if          
the image does not equal nil,   

1410
01:12:33,816 --> 01:12:37,951
in other words it has no URL    
but it does have an image,      

1411
01:12:38,020 --> 01:12:43,457
them I'm just going to use the  
information here that we have.  

1412
01:12:43,525 --> 01:12:46,660
I don't think I have to say     
self there, otherwise image,    

1413
01:12:46,729 --> 01:12:51,298
else, where are we here?        
Else if,                        

1414
01:12:51,367 --> 01:12:54,635
sorry, so                       
here I can do this, set this    

1415
01:12:54,704 --> 01:13:00,007
emojiArtBackgroundImage stuff   
using the stuff we have         

1416
01:13:00,076 --> 01:13:05,145
directly from the emoji art     
image that came through.        

1417
01:13:05,214 --> 01:13:09,883
So we just here set our         
emojiArtBackgroundImage here    

1418
01:13:09,952 --> 01:13:13,554
to be the local case            
with the imageData and          

1419
01:13:13,623 --> 01:13:18,125
the image, all right?           
Unfortunately, I also need      

1420
01:13:18,193 --> 01:13:21,729
to do this right here,          
do I have time? No, I don't,    

1421
01:13:21,798 --> 01:13:24,632
this really [LAUGH] wants to    
be put in to another function,  

1422
01:13:24,700 --> 01:13:27,468
right? You never want to copy   
and paste code like that,       

1423
01:13:27,537 --> 01:13:31,439
but we have 30 seconds left so  
I'm going to leave that. So,    

1424
01:13:31,507 --> 01:13:35,510
hopefully I did all this and    
it's gonna work, let's try,     

1425
01:13:35,578 --> 01:13:40,847
it's the world's fastest        
demo here. Okay, so             

1426
01:13:40,916 --> 01:13:43,151
I'm gonna make a new document   
since the other document        

1427
01:13:43,219 --> 01:13:45,853
is with the old style.          
So, let's go ahead and          

1428
01:13:45,922 --> 01:13:47,889
use our camera, oops, sorry.    

1429
01:13:52,595 --> 01:13:57,098
Cancel, all right, so           
I'm gonna use the camera here,  

1430
01:13:57,167 --> 01:14:00,635
let's get our fun guy           
again here, oops.               

1431
01:14:03,105 --> 01:14:07,240
There we go, zoom in on him     
a bit, we'll use that photo.    

1432
01:14:07,309 --> 01:14:10,611
So we have this photo here,     
let's put, again, a bee up      

1433
01:14:10,679 --> 01:14:15,082
here flying near the web. So    
now when we close this here,    

1434
01:14:15,151 --> 01:14:19,420
hopefully we can see            
this on other devices, so       

1435
01:14:19,489 --> 01:14:23,558
lets go over and                
run this on the simulator.      

1436
01:14:26,129 --> 01:14:28,929
All right here we go, we're on  
our simulator right here, so    

1437
01:14:28,998 --> 01:14:32,800
totally different device        
than our iPad. In fact,         

1438
01:14:32,868 --> 01:14:36,070
I'm gonna get them both on      
screen at the same time here,   

1439
01:14:36,139 --> 01:14:38,639
let's make this a little        
bit smaller. So                 

1440
01:14:38,708 --> 01:14:41,575
we've got these two different   
devices and we can see that     

1441
01:14:41,644 --> 01:14:45,512
we're on iCloud drive, that     
this document that we created   

1442
01:14:45,581 --> 01:14:48,549
right here has appeared.        
So let's open it up, and        

1443
01:14:48,618 --> 01:14:50,785
sure enough, we can see it      
with the background image,      

1444
01:14:50,853 --> 01:14:53,620
because it's not referencing    
it by the URL anymore.          

1445
01:14:53,689 --> 01:14:57,557
It actually brought the image   
that we dragged in, or in this  

1446
01:14:57,626 --> 01:15:01,828
case that we've selected with   
the camera, into our document.  

1447
01:15:01,897 --> 01:15:04,899
And we could,                   

1448
01:15:04,968 --> 01:15:07,067
put a little apple on here.     

1449
01:15:07,136 --> 01:15:10,003
And that'll save it up to       
iCloud Drive, you can see       

1450
01:15:10,072 --> 01:15:12,573
right here that it's in the     
process of uploading it. Over   

1451
01:15:12,641 --> 01:15:16,009
here, in my device, you saw     
it just download there, so,     

1452
01:15:16,078 --> 01:15:19,046
if we below here, hopefully,    
well, there we go, we have our  

1453
01:15:19,114 --> 01:15:22,382
apple, okay? So that way we're  
able to share our document      

1454
01:15:22,451 --> 01:15:25,352
across iCloud Drive, even       
though the background image     

1455
01:15:25,421 --> 01:15:28,089
was something we captured with  
a camera on a specific device.  

1456
01:15:29,125 --> 01:15:30,690
All right, so that is it for    

1457
01:15:30,759 --> 01:15:33,160
today, and                      
we'll see you next time for     

1458
01:15:33,229 --> 01:15:36,797
our very last lecture, which    
is gonna be on accessibility.   

1459
01:15:38,234 --> 01:15:38,832
>> For more,                    

1460
01:15:38,901 --> 01:15:42,203
please visit us                 
at stanford.edu.                
