dictionary - 在 Golang 中添加映射键的安全方法

Question

由于这个事实:

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.

在迭代期间将键值添加到映射是不安全的:

var m = make(map[string]int)
m["1"] = 1
m["2"] = 2
m["3"] = 3

for k, v := range m {
    if strings.EqualFold( "2", k){
        m["4"] = 4
    }
    fmt.Println(k, v)
}

有时会生成 "4" key ，有时不会。

让它始终生成的解决方法是什么？

Answer 1

使用要添加到原始 map 的项目创建另一个 map ，并在迭代后合并它们。

var m = make(map[string]int)
m["1"] = 1 
m["2"] = 2 
m["3"] = 3 

var n = make(map[string]int)

for k := range m { 
    if strings.EqualFold("2", k) {
        n["4"] = 4 
    }   
}   

for k, v := range n { 
    m[k] = v 
}   

for _, v := range m { 
    fmt.Println(v)
}