调用struct函数会给出“无法引用未导出的字段或方法". [英] Invoking struct function gives "cannot refer to unexported field or method"

问题描述

我有一个类似这样的结构:

I have a structure something like this:

type MyStruct struct {
    Id    string
}

和功能:

func (m *MyStruct) id() {
   // doing something with id here
}

我还有另一个这样的结构:

Also I have another structure like this:

type MyStruct2 struct {
    m *MyStruct
}

现在我有一个功能:

func foo(str *MyStruct2) {
    str.m.id()
}

但是我在编译时遇到了错误:

But I'm getting error in compile time:

str.m.id undefined (cannot refer to unexported field or method mypackage.(*MyStruct)."".id

如何正确调用此函数?

推荐答案

来自 http://golang.org/ref/spec# Exported_identifiers :

可以导出一个标识符以允许从另一个标识符访问它 包裹.如果同时满足以下条件，则会导出一个标识符:

An identifier may be exported to permit access to it from another package. An identifier is exported if both:

1. 标识符名称的第一个字符是 Unicode大写字母(Unicode类"Lu")；和
2. 标识符在包块中声明，或者是字段名称或方法名称.

1. the first character of the identifier's name is a Unicode upper case letter (Unicode class "Lu"); and
2. the identifier is declared in the package block or it is a field name or method name.

因此，基本上，在包外部只能使用以大写字母开头的函数/变量.

So basically only functions / variables starting with a capital letter would be usable outside the package.

示例:

type MyStruct struct {
    id    string
}

func (m *MyStruct) Id() {
   // doing something with id here
}

//then

func foo(str *MyStruct2) {
    str.m.Id()
}

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