英文:
Is a type that extends a Map still passed by reference in Go?
问题
如果在Go语言中有一个类型扩展了Map，那么这个新类型在作为函数参数时，仍然是"按引用传递"（或者说作为指针值传递）吗？还是在使用时会被复制？
示例：
type myMapType map[string][]int
func doSomething(m myMapType) myMapType{
// 做一些操作
return m
}
我想避免不必要的数据复制。所以对于上面的示例，我是否需要使用指针？
提前感谢！
英文:
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!
答案1
得分: 0
当你声明一个类型为myMapType的变量时，其行为与map[string][]int相同。
这意味着每个myMapType的实例都可以视为map[string][]int的实例，唯一的区别在于它们的类型在某些情况下不被认为是“相同的”（如赋值、类型切换、类型断言等）。
换句话说，myMapType和map[string][]int是等价的，但不是相同的。
英文:
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.
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