loops - 如何在范围循环中添加到 map 中

Question

package main

import (
    "fmt"
)

func main() {
    m := make(map[int]int, 4)
    m[1] = 0
    m[2] = 0
    for k, _ := range m {
        i := 10 + k
        m[i] = 0
    }
    fmt.Println(m)
    fmt.Println("len:", len(m))
}

此代码返回:8 或 10 或 6 作为循环后 map 的长度。视频是here , Playground here .

我看到新添加的元素进入了范围，但无法解释为什么这个循环随机停止？

Answer 1

Spec: For statements:

The iteration order over maps is not specified and is not guaranteed to be the same from one iteration to the next. If a map entry that has not yet been reached is removed during iteration, the corresponding iteration value will not be produced. If a map entry is created during iteration, that entry may be produced during the iteration or may be skipped. The choice may vary for each entry created and from one iteration to the next. If the map is nil, the number of iterations is 0.

规范指出，如果您将条目添加到您正在测距的 map 中，您添加的元素可能会或可能不会被循环访问，而且，被访问的元素甚至不是确定性的(再次执行时可能会改变).