怎么知道接口的功能没有实现? [英] How to known a function of a interface is not realized?

问题描述

我刚刚在Go中尝试了以下代码.

I just tried the following code in Go.

package main

type inter interface {
    aaa() int
}

type impl struct {
    inter
}

func main() {
    var a inter
    a = impl{}
    // how to check the function for interface `inter` is not realized?
    a.aaa()
}

可以是 go build 和 go run .但会收到类似的恐慌:

It can be go build and go run. But will receive a panic like:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0xffffffff addr=0x0 pc=0x8972c]

goroutine 1 [running]:
main.(*impl).aaa(0x40c018, 0x41a788, 0xb2ae0, 0x40c018)
    <autogenerated>:1 +0x2c
main.main()
    /tmp/sandbox029518300/prog.go:15 +0x60

我怎么知道 a.aaa()没有实现.

推荐答案

变量 a 的类型为 inter ，该接口指向impl .结构 impl 中嵌入了 inter 接口.这意味着 impl.aaa()存在，实际上意味着 impl.inter.aaa().但是，在您的代码中， impl.inter 为零.为了更清楚一点:

The variable a is of type inter, an interface, which is pointing to an impl. The struct impl has the inter interface embedded in it. That means impl.aaa() exists, which actually means impl.inter.aaa(). However in your code impl.inter is nil. To make it more clear:

b:=impl{}
var a inter
a=b
a.aaa() // this will call b.inter.aaa(), but b.inter is nil

这篇关于怎么知道接口的功能没有实现?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！