我们先来看一道面试题:以下代码能编译过去吗?为什么?
- package main
- import (
- "fmt"
- )
- type People interface {
- Speak(string) string
- }
- type Stduent struct{}
- func (stu *Stduent) Speak(think string) (talk string) {
- if think == "bitch" {
- talk = "You are a good boy"
- } else {
- talk = "hi"
- }
- return
- }
- func main() {
- var peo People = Stduent{}
- think := "bitch"
- fmt.Println(peo.Speak(think))
- }
答案是不能,提示Stduent does not implement People (Speak method has pointer receiver),修正方法是var peo People = &Stduent{},赋值为指针
在Go语言中,函数和方法是不一样的,函数是没有接收者的,而方法是有接收者的,属于某个结构体。
接受者有两种:value receivers(按值传递),pointer receivers(按指针传递,可能改变传入的参数)
之前看到有地方解释道:pointer receivers的方法既能传值也能传指针,包含了value receivers的方法。
这个理解是错误的。
从这道题来看不是这样的,value receivers和pointer receivers是有明确区分的,people interface是value receivers,而student实现了pointer receivers的speak方法,所以student没有实现peple。
事实上pointer receivers的方法只是将m.speak()自动转换为(&m).speak(),这点官方的go tour中就有提到,go编译器帮你省去了取地址的一步。