两种不同的类型如何使用接口在golang中实现相同的方法？

Question

Say I have two structs:

type First struct {
    str string
}
type Second struct {
    str string
}

And I want both of them to implement interface A:

type A interface {
    PrintStr() //print First.str or Second.str
}

It seems redundant to have an implementation for both First and Second structs like so:

func (f First) PrintStr() {
    fmt.Print(f.str)
}

func (s Second) PrintStr() {
    fmt.Print(s.str)
}

Is there a way I can have one implementation for all the structs implementing interface A? Something like this, but it doesn't seem to work:

func (a A) PrintStr() {
    fmt.Print(a.str)
}

Thank you!

Answer 1

No you can't, but you could create a base type and then embed it into your 2 struct, therefore only needing an implementation for the base type:

type WithString struct {
    str string
}

type First struct {
    WithString
}

type Second struct {
    WithString
}

type A interface {
    PrintStr() //print First.str or Second.str
}

func (w WithString) PrintStr() {
    fmt.Print(w.str)
}

Usage:

a := First{
    WithString: WithString{
        str: "foo",
    },
}

Complete Example on Playground

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