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<script src="highlight.pack.js"></script> <script>hljs.initHighlightingOnLoad();</script> ## Accessing rails scope objects:

{% highlight ruby %} ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday'].each do |wkd| @class_sessions.send(wkd) end {% endhighlight %}

Kill rails process in cmd

lsof -wni tcp:3000

This will return PID number and other information of the process

kill -9 PID

Use Prawn gem to generate pdf

Draw a dash line:

{% highlight ruby %} dash(4, :space => 4, :phase => 1) stroke_horizontal_line 0, 500 {% endhighlight %}

Change back to solid line:

{% highlight ruby %} undash() {% endhighlight %}

then

{% highlight ruby %} stroke_horizontal_line 0, 500 {% endhighlight %}

Setting dash line will result in dash lines in following tables. Without using undash(), the following tables will have dash lines as well.

Use gem combine_pdf to combine pdf files

After using Prawn to generate two pdf files, I used gem combine_pdf to combine them together.

The simplest example:

{% highlight ruby %} pdf1 = Invoice.new(student, class_sessions) pdf2 = Receipt.new(student, class_sessions) pdf = CombinePDF.new pdf << CombinePDF.parse(pdf1.render) pdf << CombinePDF.parse(pdf2.render) {% endhighlight%}

To save the file:

{% highlight ruby %} pdf.save "combine.pdf" {% endhighlight%}

To display the file in browser:

{% highlight ruby %} respond_to do |format| format.pdf do send_data pdf.to_pdf, :filename => "combine.pdf", :type => "application/pdf", :disposition => "inline" end end {% endhighlight%}

Hint: When I use send_data pdf, :filename => "combine.pdf", :type => "application/pdf", :disposition => "inline", the browser gives error loading pdf file. The reason is, pdf is the object, while pdf.to_pdf is the PDF file stream that could be displayed.

Set indentation of Sublime Text 3

To set indentation to two spaces, we can simply click view -> indentation to set. But this can only change the setting for the current tab.
To change the default setting, click Sublime Text -> Preferences -> Settings Default, this file is the default setting, users are not supposed to change it. We can copy its content, and paste it to Sublime Text -> Preferences -> Settings User. Find the indentation settings and change it:

"tab_size": 2,
"translate_tabs_to_spaces": true,

The setting sometimes does not work because it only works for chosen languages. For example, when I did this setting, I was opening a ruby file. After I saved the settings, I found it does not work on haml files. To make the setting apply to haml, first open an haml file, then click Sublime Text -> Preferences -> Settings -> More -> Syntax Specific -> User. Copy the above setting code into the file and save. Repeat this action if some other languages files need to be set.

Set encoding while import csv files

The previous encoding code:

{% highlight ruby %} CSV.parse(csv,skip_blanks: true, headers:true, return_headers: false,encoding:"iso-8859-1").each do |row| ... end {% endhighlight%}

There are invalid characters in the csv file. We can replace these characters with "".

{% highlight ruby %} CSV.parse(csv.encode!("utf-8", "iso-8859-1", invalid: :replace, replace: ''), headers: true, skip_blanks: true, return_headers: false).each do |row| ... end {% endhighlight%}

Using delayed_job in Rails application

Add gem into gemfile:

{% highlight ruby %} gem 'delayed_job' gem 'delayed_job_active_record' {% endhighlight%}

Create model and database table for delayed job:

{% highlight ruby %} rails g delayed_job:active_record rake db:migrate {% endhighlight%}

Using gem sidekiq to run long time jobs in background and sidekiq_status to track job status

Jobs could be done using Worker in sidekiq. Example code: Create a worker ruby file in app/workers folder

{% highlight ruby %} class MyWorker include SidekiqStatus::Worker def perform(variable) do something... end end {% endhighlight%}

Note that perform is an instance method, whereas perform_async is called on the class.
In controller:

{% highlight ruby %} jid = MyWorker.perform_async(variable) {% endhighlight%}

Note: To make any changes on the perform method or any other methods which are performed by sidekiq, the sidekiq server should be restarted to make the changes apply.

jid is the job id which is returned by the perform_async method. It can be used to track the job status.

{% highlight ruby %} container = SidekiqStatus::Container.load(jid) container.status # => 'working' container.at # => 50 container.total # => 200 container.pct_complete # => 25 container.message # => 'Processing object #{50}' {% endhighlight%}

Compress multiple files to zip and providing downloading in Rails

{% highlight ruby %} require 'rubygems' require 'zip' m = params[:month].to_i if m > 8 y_m = "#{Date::MONTHNAMES[m]} #{CurrentYear.first.year}" else y_m = "#{Date::MONTHNAMES[m]} #{CurrentYear.first.year+1}" end @paperclip_objects = xxx t = Tempfile.new('tmp-zip-' + request.remote_ip) Zip::OutputStream.open(t.path) do |zos| @paperclip_objects.each do |i| zos.put_next_entry(i.pdf_file_name) zos.print IO.read(i.pdf.path) end end send_file t.path, :type => "application/zip", :filename => "myzip.zip" t.close {% endhighlight%}

Hint: pdf is the attachment field in the objects. This piece of code uses Tempfile so these files could be deleted when calling close.

Pass parameters in link_to

{% highlight ruby %} = link_to 'button', my_controller_path(a: 123, b: 321), class: 'btn' {% endhighlight%}

In controller: {% highlight ruby %} @a_value = params[:a] {% endhighlight%}

Pass parameters in render

{% highlight ruby %} = render 'form', contact_us: @contact_us, product_id: @product_id {% endhighlight%}

In _form.html.haml: {% highlight ruby %} = simple_form_for contact_us, url: contact_path, .... %p= product_id {% endhighlight%}