golang-101-hacks(10)——String

注：本文是对golang-101-hacks中文翻译。
在Go中string是由不可变的字节数组构成的。一旦赋值，就不能修改字符串的值。例如
In Go, string is an immutable array of bytes. So if created, we can't change its value. E.g.:

package main

func main()  {
    s := "Hello"
    s[0] = 'h'
}

编译结果会提示错误：
The compiler will complain:

cannot assign to s[0] 

对字符串的修改可以将其转换为“byte”数组。但是实际上您并没有对原始字符串进行修改操作，改变的只是一个原始字符串的副本。

To modify the content of a string, you could convert it to a byte array. But in fact, you do not operate on the original string, just a copy:

package main

import "fmt"

func main()  {
    s := "Hello"
    b := []byte(s)
    b[0] = 'h'
    fmt.Printf("%s\n", b)
} 

运行结果
The result is like this:

hello

Go使用的是UTF-8的编码方式，函数len的结果是当前字符字节的长度而不是字符长度
Since Go uses UTF-8 encoding, you must remember the len function will return the string's byte number, not character number:

package main

import "fmt"

func main()  {
    s := "日志log"
    fmt.Println(len(s))
} 

执行结果是
The result is:

9

由于每个中文占3个字节，上面的例子中s字符串有5个字符和9个字节组成的
Because each Chinese character occupied 3 bytes, s in the above example contains 5 characters and 9 bytes.
对字符串执行for ... range循环语句可以获取到每个字符
If you want to access every character, for ... range loop can give a help:

package main
import "fmt"

func main() {
    s := "日志log"
    for index, runeValue := range s {
        fmt.Printf("%#U starts at byte position %d\n", runeValue, index)
    }
}

执行结果

U+65E5 '日' starts at byte position 0
U+5FD7 '志' starts at byte position 3
U+006C 'l' starts at byte position 6
U+006F 'o' starts at byte position 7
U+0067 'g' starts at byte position 8

参考
Strings, bytes, runes and characters in Go;
The Go Programming Language.