为什么Go输入nil? [英] Why does Go have typed nil?

问题描述

为什么Go会输入 nil ?为了方便起见，它会抛出一个显式的接口构象检查.无类型的 nil 有什么问题?设计人员要解决什么类型的 nil ?

Why does Go have typed nil? It throws an explicit interface conformation check for convenience. What's the problem of untyped nil and what did the designers want to solve with typed nil?

推荐答案

听起来您正在询问以下错误消息:

It sounds like you're asking about this error message:

http://play.golang.org/p/h80rmDYCTI

package main

import "fmt"

type A struct {}
type B struct {}

func (a *A) Foo() {
    fmt.Println("A")
}

func (b *B) Foo() {
    fmt.Println("B")
}

func main() {
    n := nil
    n.Foo()
}

此打印:

prog.go:17: use of untyped nil
 [process exited with non-zero status]

在该示例中，程序应打印"A"还是"B"?

In that example, should the program print "A" or "B"?

您必须帮助编译器做出决定.您可以通过指定 n 的类型来做到这一点.

You have to help the compiler decide. The way you do that is by specifying the type of n.

例如:

http://play.golang.org/p/zMxUFYgxpy

func main() {
    var n *A
    n.Foo()
}

打印"A".

在其他语言中，如果 n 为 nil 或等效值， n.Foo()可能会立即崩溃.Go的语言设计师决定让您确定应该怎么做.如果在不检查 nil 的情况下访问该指针，则会得到与其他语言相同的行为.

In other languages, n.Foo() might crash immediately if n is nil or its equivalent. Go's language designers decided to let you determine what should happen instead. If you access the pointer without checking for nil, you get the same behavior as in other languages.

这篇关于为什么Go输入nil?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！