尽管映射总是引用类型，但如果它们是从非指针接收器返回的呢？

Question

Supposedly maps are reference types in Go, so when returning them from functions, you don't need to pass as a pointer to the map in order for the changes to be visible outside the function body. But what if said map is returned from a method on a non-pointer struct?

For example:

type ExampleMapHolder struct {
    theUnexportedMap map[string]int
}

func (emp ExampleMapHolder) TheMap() map[string]int {
    return emp.theUnexportedMap
}

If I make a call to TheMap() , and then modify a value in it, will this change be visible elsewhere even though the receiver is not a pointer? I imagine it would return a reference to a map that belonged to a copy of ExampleMapHolder, but haven't been able to find an explicit answer in the docs.

Answer 1

Why won't you just check it?

emp := ExampleMapHolder{make(map[string]int)}
m := emp.TheMap()
m["a"] = 1
fmt.Println(emp) // Prints {map[a:1]}

Playground: http://play.golang.org/p/jGZqFr97_y