为什么golang行为中的字符串指针在范围循环中与直觉相反? [英] Why is string pointer in golang behavior counter-intuitive in range-loop?

问题描述

使用以下代码: https://play.golang.org/p/tCm1W-K-6ob

此代码将打印: [c c c] ，但 [a b c] 除外.

This code would print: [c c c], but [a b c] is excepted.

type A struct {
    a *string
}

func f() {
    slist := []string{"a", "b", "c"}
    list := make([]*A, len(slist))
    for i, v := range slist {
        item := &A{
            a: &v,
        }
        list[i] = item
    }
    fmt.Printf("[%s %s %s]", *list[0].a, *list[1].a, *list[2].a)
}

func main() {
    f()
}

为什么列表不是 ["a"，"b"，"c"] ?范围或& string 发生了什么事?

Why the list is not ["a", "b", "c"]? What happened to the range or the &string?

推荐答案

所有项均包含一个局部变量 v 的地址.

The items all contain the address of the one local variable v.

如果您的目标是在 a 字段中分配slice元素的地址，请执行以下操作:

If your goal is to assign the address of the slice element the a field, then do the following:

for i := range slist {
    item := &A{
        a: &slist[i],  // address of element instead of local variable.
    }
    list[i] = item
}

在围棋场上运行.

您还可以通过在每次循环迭代中创建一个新变量来获得所需的输出:

You can also get the output you want by creating a new variable on each loop iteration:

for i, v := range slist {
    v := v  // create new value on each iteration.
    item := &A{
        a: &v,
    }
    list[i] = item
}

在围棋场上运行.

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