C++ 中嵌套类型/类的前向声明

问题描述

我最近陷入了这样的境地:

I recently got stuck in a situation like this:

class A
{
public:
    typedef struct/class {…} B;
…
    C::D *someField;
}

class C
{
public:
    typedef struct/class {…} D;
…
    A::B *someField;
}

通常你可以声明一个类名:

Usually you can declare a class name:

class A;

但是不能前向声明嵌套类型，以下会导致编译错误.

But you can't forward declare a nested type, the following causes compilation error.

class C::D;

有什么想法吗?

推荐答案

你做不到，这是 C++ 语言的一个漏洞.您必须取消嵌套至少一个嵌套类.

You can't do it, it's a hole in the C++ language. You'll have to un-nest at least one of the nested classes.

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