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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