Go string operation

go String manipulation

Go A string in a language is a byte slice . Put the content in double quotation marks ”” Between , also Go The string in is compatible Unicode Coded , And use UTF-8 Encoding . Because the string is a byte slice , So we can get every byte of the string .

func main() {
    
	s := "hello world"
	for i:=0;i<len(s);i++{
    
		fmt.Println(string(s[i]))  //  No addition  string  What is printed out is the corresponding character  Unicode  code 
	}
}

rune

for Loop string , The default is a byte by byte cycle , But our Chinese is 3 Bytes correspond to a Chinese character , therefore , Direct circular Chinese , It will cause garbled code

func main() {
    
	s1 := " China "

	for i:=0;i<len(s1);i++{
    
		fmt.Print(string(s1[i])) // 中国
	}
}

therefore , When Chinese appears in the string , To prevent garbled code , You can make strings rune(int32) Slice of for loop

func main() {
    
	s := " in   countries "
	r := []rune(s)
	for i:=0;i<len(r);i++{
    
		fmt.Print(string(r[i]))  //  in   countries 
	}
}

byte Slicing and rune Slice build string

since go The underlying storage string is stored byte, So can we directly create a slice , Put bytes in the slice .

The answer is obviously yes .

"hello world"  Decimal bytes are  104 101 108 108 111 32 119 111 114 108 100  You can also put 16 Base number 

func main() {
    
	byteSlice := []byte{
    104,101,108,108,111,32,119,111,114,108,100}
	str := string(byteSlice)
	fmt.Println(str)  // hello world
}

Again , You can also create rune Slice to build Chinese characters

" in   countries "  Decimal bytes are  20013 32 22269 
func main() {
    
	runeSlice := []rune{
    20013,32,22269 } // 32 Refers to the space 
	str := string(runeSlice)
	fmt.Println(str) //  in   countries 
}

byte(uint8,  A byte )  and  rune(int32,  Four bytes )  These two types , To represent bytes and strings 

String length

String length statistics , stay python Can be used in the len Methods to count , Also in go in , There is also a built-in function len(), But this len() stay go What is counted in is the number of bytes of the string , The reason is also go The string in is a byte stored . The statistics of the length of characters need to be used go Another built-in function in utf8.RuneCountInString(), The case is as follows :

func main() {
    

	s := "a China "
	fmt.Println(len(s))    //  The statistics are byte length 
	fmt.Println(utf8.RuneCountInString(s))  //  Count character length 
}

How to modify the string

We mentioned that earlier , The string is in go Is a value type , Although it can be retrieved by index , However, it is forbidden to modify the value according to the index

func main(){
    
	s := "hello"
	fmt.Println(string(s[0]))  // h
    s[0] = 'a'  //  Report errors ,' '  Is to get this character Unicode code 
}	

So if we want to change the string , It can also be achieved by slicing , But the original string is still unchanged ！

func main() {
    
	s := "hello"
	r := []rune(s)
	r[1] = 'A'
	fmt.Println(string(r)) // hAllo
	fmt.Println(s)		// hello
}