07.6.md

7.6 Strings

Almost everything we see is represented by string, so it's a very important part of web development, including user inputs, database access; also we need to split, join and convert strings in many cases. In this section, we are going to introduce packages strings and strconv in Go standard library.

strings

Following functions are from package strings, more details please see official documentation:

• func Contains(s, substr string) bool

  Check if string s contains string substr, returns 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 with 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 means replication times, if n less than 0 means replace all.

    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 in to a slice.

    fmt.Printf("Fields are: %q", strings.Fields("  foo bar  baz   "))
    //Output:Fields are: ["foo" "bar" "baz"]

strconv

Following functions are from package strconv, more details please see official documentation:

• 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 type data to 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 string 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, err := strconv.Itoa("1023")
    	if err != nil {
    		fmt.Println(err)
    	}
    	fmt.Println(a, b, c, d, e)
    }

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