为什么方法签名必须与接口方法完全匹配 [英] Why does method signature have to perfectly match interface method

问题描述

我开始学习Go，但在理解以下内容时遇到了困难:

I began to learn Go and have trouble understanding the following:

package main

import "fmt"

type I interface {
    foo(interface {})
}

type S struct {}

func (s S) foo(i int) {
    fmt.Println(i)
}

func main() {
    var i I = S{}
    i.foo(2)
}

此操作失败，并显示以下信息:

This fails with:

cannot use S literal (type S) as type I in assignment:
        S does not implement I (wrong type for foo method)
                have foo(int)
                want foo(interface {})

鉴于 int 实现了 interface {} 的事实，我不明白为什么Go不接受 foo(int)签名.谁能帮忙解释一下?

I don't understand why Go doesn't accept the foo(int) signature given the fact that int implements interface {}. Can anyone help with an explanation?

推荐答案

我认为您对界面的理解不够充分.Interface {}本身就是一种类型.它由两部分组成:基础类型和基础值.

I think your understanding of interface isn't sound. Interface{} itself is a type. It consists of two things : underlying type and underlying value.

Golang没有重载.Golang类型系统按名称匹配，并且要求类型保持一致

Golang doesn't have overloading. Golang type system matches by name and requires consistency in the types

因此，当您定义以接口类型作为参数的函数时:

So, when you are defining a function taking a interface type as a parameter:

foo(interface {})

这与采用int类型的函数不同:

This is a different function from a function taking int type:

foo(int)

因此，您应将以下行更改为

So you should change the following line to

func (s S) foo(i interface{}) {
    fmt.Println(i)
}

或更妙的是:

type I interface {
    foo()
}

type S struct {
    I int
}

func (s S) foo() {
    fmt.Println(s.I)
}

func main() {
    var i I = S{2}
    i.foo()
}

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