On the web, almost everything we see (including user inputs, database access, etc.), is represented by strings. They are a very important part of web development. In many cases, we also need to split, join, convert and otherwise manipulate strings. In this section, we are going to introduce the strings
and strconv
packages from the Go standard library.
The following functions are from the strings
package. See the official documentation for more details:
-
func Contains(s, substr string) bool
Check if string
s
contains stringsubstr
, returns a boolean value.
fmt.Println(strings.Contains("seafood", "foo"))
fmt.Println(strings.Contains("seafood", "bar"))
fmt.Println(strings.Contains("seafood", ""))
fmt.Println(strings.Contains("", ""))
//Output:
//true
//false
//true
//true
-
func Join(a []string, sep string) string
Combine strings from slice with separator
sep
.
s := []string{"foo", "bar", "baz"}
fmt.Println(strings.Join(s, ", "))
//Output:foo, bar, baz
-
func Index(s, sep string) int
Find index of
sep
in strings
, returns -1 if it's not found.
fmt.Println(strings.Index("chicken", "ken"))
fmt.Println(strings.Index("chicken", "dmr"))
//Output:4
//-1
-
func Repeat(s string, count int) string
Repeat string
s
count
times.
fmt.Println("ba" + strings.Repeat("na", 2))
//Output:banana
-
func Replace(s, old, new string, n int) string
Replace string
old
with stringnew
in strings
.n
is the number of replacements. If n is less than 0, replace all instances.
fmt.Println(strings.Replace("oink oink oink", "k", "ky", 2))
fmt.Println(strings.Replace("oink oink oink", "oink", "moo", -1))
//Output:oinky oinky oink
//moo moo moo
-
func Split(s, sep string) []string
Split string
s
with separatorsep
into a slice.
fmt.Printf("%q\n", strings.Split("a,b,c", ","))
fmt.Printf("%q\n", strings.Split("a man a plan a canal panama", "a "))
fmt.Printf("%q\n", strings.Split(" xyz ", ""))
fmt.Printf("%q\n", strings.Split("", "Bernardo O'Higgins"))
//Output:["a" "b" "c"]
//["" "man " "plan " "canal panama"]
//[" " "x" "y" "z" " "]
//[""]
-
func Trim(s string, cutset string) string
Remove
cutset
of strings
if it's leftmost or rightmost.
fmt.Printf("[%q]", strings.Trim(" !!! Achtung !!! ", "! "))
Output:["Achtung"]
-
func Fields(s string) []string
Remove space items and split string with space into a slice.
fmt.Printf("Fields are: %q", strings.Fields(" foo bar baz "))
//Output:Fields are: ["foo" "bar" "baz"]
The following functions are from the strconv
package. As usual, please see official documentation for more details:
- Append series, convert data to string, and append to current byte slice.
package main
import (
"fmt"
"strconv"
)
func main() {
str := make([]byte, 0, 100)
str = strconv.AppendInt(str, 4567, 10)
str = strconv.AppendBool(str, false)
str = strconv.AppendQuote(str, "abcdefg")
str = strconv.AppendQuoteRune(str, '单')
fmt.Println(string(str))
}
- Format series, convert other data types into string.
package main
import (
"fmt"
"strconv"
)
func main() {
a := strconv.FormatBool(false)
b := strconv.FormatFloat(123.23, 'g', 12, 64)
c := strconv.FormatInt(1234, 10)
d := strconv.FormatUint(12345, 10)
e := strconv.Itoa(1023)
fmt.Println(a, b, c, d, e)
}
- Parse series, convert strings to other types.
package main
import (
"fmt"
"strconv"
)
func main() {
a, err := strconv.ParseBool("false")
if err != nil {
fmt.Println(err)
}
b, err := strconv.ParseFloat("123.23", 64)
if err != nil {
fmt.Println(err)
}
c, err := strconv.ParseInt("1234", 10, 64)
if err != nil {
fmt.Println(err)
}
d, err := strconv.ParseUint("12345", 10, 64)
if err != nil {
fmt.Println(err)
}
e := strconv.Itoa(1023)
fmt.Println(a, b, c, d, e)
}