覆盖全局变量

Question

我想知道为什么以下代码中没有警告或错误允许我覆盖全局变量。

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package main

import "fmt"

type MyStruct struct {

    MyInt uint32

}

func (s *MyStruct) MyMethod() {

    fmt.Println(s.MyInt)

}

var theStruct MyStruct

func main() {

    // Override the above global variable

    // I would expect some kind of warning or error here?

    theStruct := MyStruct {

        MyInt: 42,

    }

    // Outputs 42

    theStruct.MyMethod()

    // Outputs 0

    UseMyStruct()

}

func UseMyStruct() {

    theStruct.MyMethod()

}

Answer 1

变量可以隐藏父作用域中的其他变量。在您的示例中，范围层次结构如下所示：global (scope)├── theStruct (variable)└── main (scope)    └── theStruct (variable)像这样的阴影通常是通过以下方式完成的err：package mainimport (    "io/ioutil"    "log")func main() {    f, err := ioutil.TempFile("", "")    if err != nil {        log.Fatal(err)    }    defer f.Close()    // This err shadows the one above, it is technically in its    // own scope within the "if".    if _, err := f.Write([]byte("hello world\n")); err != nil {        log.Fatal(err)    }    if true {        // We can even shadow with different types!        err := 3        log.Println(err)    }}