尝试在Go中实现地图合并功能，但失败

Question

Most simple reproduction of the issue:

package main

import "fmt"

type stringMap map[int]string

func (s *stringMap) Merge(m stringMap) {
    for key, value := range m {
        s[key] = value
    }
}

func main() {
    myMap := stringMap{1: "a", 2: "b"}
    myMap.Merge(stringMap{3: "c"})
    fmt.Println(myMap)
}

Why I can't use key variable as a key on mymap stringMap?

Playground: http://play.golang.org/p/mSprMXq5QF

Answer 1

You can't using indexing (accessing the map) on a pointer to a map.

You just have to make the following change (pay noticed to the removed *):

func (s stringMap) Merge(m stringMap) { ... }