扩展 Map 的类型是否仍然在 Go 中通过引用传递？

Question

If you have a type in Go, that extends a Map, is this new type still "passed by reference" (or respectively passed as a pointer value)? Or is it copied when used as a function parameter?

Example:

type myMapType map[string][]int

func doSomething(m myMapType) myMapType{

// do something
return m
}

I want to prevent unnecessary copying of data. So do I need a pointer for the above example, or not?

Thanks in advance!

Answer 1

When you declare

type myMapType map[string][]int

You now have a type called myMapType , whose behaviour is the same as map[string][]int .

It's the same as if every instance of myMapType was an instance of map[string][]int , with the only difference being that their types are not considered "the same" in cases where that matters (assignment, type switch, type assertion, etc.).

In other words, myMapType and map[string][]int are equi-valent but not identic-al .