英文:
Why character switching in string is not allowed in Golang?
问题
我理解Go语言中的字符串实际上是一个字节的数组。为什么不允许使用str[0] = str[1]的赋值操作呢？谢谢！
str := "hello"str[0] = str[1]// 期望的结果是 eello<details><summary>英文:</summary>I understand that Go string is basically an array of byte. What is the explanation why str[0] = str[1] is not allowed? Thanks!
str := "hello"
str[0] = str[1]
// expecting eello
答案1
得分: 3
我理解到Go语言中的字符串基本上是一个字节数组。
不完全正确。一个字符串由以下组成：
- 指向一个字节数组的指针，
- 一个对应于该数组长度的整数。
如果你可以更新给定字符串变量中的单个符文（rune），那么字符串将是可变的，这与Go语言设计者的意愿相悖（参考：https://golang.org/ref/spec#String_types）：
字符串是不可变的：一旦创建，就无法更改字符串的内容。
请参阅golang.org博客上的这篇文章（https://go.dev/blog/strings）：
在Go语言中，字符串实际上是一个只读的字节切片。
不可变性有很多优点，比如易于推理，但它也可能被视为一种麻烦。当然，覆盖一个字符串变量是合法的：
str := "hello"str = "eello"
此外，你始终可以将字符串转换为可变的数据结构（即[]byte或[]rune），进行所需的更改，然后再将结果转换回字符串。
str := "hello"fmt.Println(str)bs := []byte(str)bs[0] = bs[1]str = string(bs)fmt.Println(str)
输出：
helloeello
然而，要注意这样做涉及到复制操作，如果字符串很长和/或重复进行此操作，可能会影响性能。
英文:
> I understand that Go string is basically an array of bytes.
Not exactly. A string is made up of
- a pointer to an array of bytes, and
- an integer that corresponds to the length of that array.
If you could update individual runes of a given string variable, then strings would be mutable, against the wishes of the Go designers:
> Strings are immutable: once created, it is impossible to change the contents of a string.
See also this post on the golang.org blog:
> In Go, a string is in effect a read-only slice of bytes.
Immutability has many advantages—for one thing, it's easy to reason about—but it can be perceived as a nuisance. Of course, overwriting a string variable is legal:
str := "hello"str = "eello"
Moreover, you can always convert the string to a data structure that is mutable (i.e. a []byte or a []rune), make the required changes, and then convert the result back to a string.
str := "hello"fmt.Println(str)bs := []byte(str)bs[0] = bs[1]str = string(bs)fmt.Println(str)
Output:
helloeello
However, be aware that doing so involves copying, which can hurt performance if the string is long and/or if it's done repeatedly.
答案2
得分: 0
Go字符串是不可变的，并且表现得像只读的字节切片。要更新数据，请使用rune切片代替。
package mainimport ("fmt")func main() {str := "hello"fmt.Println(str)buf := []rune(str)buf[0] = buf[1]s := string(buf)fmt.Println(s)}
输出：
helloeello
英文:
Go strings are immutable and behave like read-only byte slices,To update the data, use a rune slice instead;
package mainimport ("fmt")func main() {str := "hello"fmt.Println(str)buf := []rune(str)buf[0] = buf[1]s := string(buf)fmt.Println(s)}
Output:
helloeello
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