什么是c ++中的forward declaration？ [英] What is forward declaration in c++?

问题描述

此回答说： / p>

This answer says:

...最后，

… Finally,

typedef struct { ... } Foo;

声明一个匿名结构并为其创建一个typedef。因此，使用此构造，它在标签命名空间中没有名称，只有typedef命名空间中的名称。这意味着它也不能被前向声明。

declares an anonymous structure and creates a typedef for it. Thus, with this construct, it doesn't have a name in the tag namespace, only a name in the typedef namespace. This means it also can't be forward-declared. If you want to make a forward declaration, you have to give it a name in the tag namespace.

什么是转发声明？

推荐答案

Chad给出了一个非常好的字典定义。转发声明通常在C ++中用于处理循环关系。例如：

Chad has given a pretty good dictionary definition. Forward declarations are often used in C++ to deal with circular relationships. For example:

class B; // Forward declaration

class A
{
    B* b;
};

class B
{
    A* a;
};

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