Golang Learning notes-1.15 strings

This is the 15th chapter of Golang Language Learning Tutorial

What is a string

The string in the Go language is a byte slice. You can create a string by placing the contents between double quotes.

package mainimport "fmt"func main() {  name := "hello world"  fmt.Println(name)}

Program output:hello world
The string in Go is Unicode-encoded and encoded using UTF-8.

Get each byte of a string separately

Because the string is a byte slice, you can get every byte of a string.

package mainimport "fmt"func printbytes(s string) {  //定义函数    for i := 0; i < len(s); i++ {   //len(s) 返回字符串中字符的数量        fmt.Printf( "%x ", s[i])   //%x 指定打印字符串的16进制编码    }}func printchars(s string) {    for i := 0; i< len(s); i++ {        fmt.Printf("%c ", s[i])   //%c  指定打印字符串的字符    }}func main() {    name := "hello world"    printbytes(name)    fmt.Println("\n")    printchars(name)}

In the above program, Len (s) is used to return the number of characters in a string,%x specifies the 16 encoding of the printed string, and%c is used to specify the number of printed strings.
The above program output is:

6c 6c 6f, 6f, 6c 64
H e l l o w o R l D

The above program gets each character of the string, although it appears to be legal, but there is a serious bug. Let me break this code down to see what we did wrong.

package mainimport "fmt"func printbytes(s string) {  //定义函数    for i := 0; i < len(s); i++ {   //len(s) 返回字符串中字符的数量        fmt.Printf( "%x ", s[i])   //%x 指定打印字符串的16进制编码    }}func printchars(s string) {    for i := 0; i< len(s); i++ {        fmt.Printf("%c ", s[i])   //%c  指定打印字符串的字符    }}func main() {    name := "hello world"    printbytes(name)    fmt.Println("\n")    printchars(name)    name = "Señor"      fmt.Println("\n")    printchars(name)}

In the above program, we try to output Señor characters, but output the wrong S eã±o R. Why did the program split up Hello World perfectly, but Señor the segmentation was wrong? This is because ñ the Unicode code point is U+00F1 . Its UTF-8 encoding takes up two bytes of C3 and B1. Its UTF-8 encoding takes up two bytes of C3 and B1. When we print the characters, it is wrong to assume that each character's encoding will only occupy one byte. In UTF-8 encoding, a code point may occupy more than one byte of space. So what do we do? Rune can help us solve this problem.

Rune

Rune is the built-in type of Go language, and it is also a nickname for Int32. In the Go language, Rune represents a code point. Code points can be represented by a rune, regardless of the number of bytes consumed. Let's change the program above and use Rune to print characters.

package mainimport "fmt"func printbytes(s string) {  //定义函数    for i := 0; i < len(s); i++ {   //len(s) 返回字符串中字符的数量        fmt.Printf( "%x ", s[i])   //%x 指定打印字符串的16进制编码    }}func printchars(s string) {    runes := []rune(s)  //字符串被转化为一个 rune 切片    for i := 0; i< len(s); i++ {        fmt.Printf("%c ", runes[i])   //%c  指定打印字符串的字符    }}func main() {    name := "hello world"    printbytes(name)    fmt.Println("\n")    printchars(name)    name = "Señor"    fmt.Println("\n")    printchars(name)}

In the above program, the string is converted into a rune slice.
The program output is:

6c 6c 6f, 6f, 6c 64
H e l l o w o R l D
S Eño R

The string is immutable

The string in go is immutable and cannot be changed once created:

package mainimport (      "fmt")func mutate(s string)string {      s[0] = 'a'//any valid unicode character within single quote is a rune     return s}func main() {      h := "hello"    fmt.Println(mutate(h))}

In the above program want to change the first character of H into a, but error: main.go:8: cannot assign to s[0] , it can be seen that the string is not allowed to modify.

To modify a string, you can convert the string into a rune slice. The slice can then make any desired changes and then convert to a string.

package mainimport (      "fmt")func mutate(s []rune) string {      s[0] = 'a'     return string(s)}func main() {      h := "hello"    fmt.Println(mutate([]rune(h)))}

In the above program, the function mutate receives an incoming rune slice, changes the first character to a, and then converts it to a string output. So the above program output is:aello

Above for learning Golang String Chapter