en/07.6.md
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 string substr, 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 string s, 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 string new in string s. 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 separator sep 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 string s 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:
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))
}
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)
}
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)
}