在C ++中处理共同依赖类的最好方法是什么？ [英] What is the best way to deal with co-dependent classes in C++?

问题描述

说我有一个类foo，其中有一个类bar的对象作为成员

Say I have a class foo with an object of class bar as a member

class foo
{
    bar m_bar;
};

现在假设bar需要跟踪拥有它的foo。

Now suppose bar needs to keep track of the foo that owns it

class bar
{
    foo * m_pfoo;
}

这两个类相互引用，没有前向声明，所以在foo的声明之前添加这一行解决了这个问题

The two classes reference each other and without a forward declaration, will not compile. So adding this line before foo's declaration solves that problem

class bar;

现在，这里是问题 - 当写头文件时，每个 >依赖于另一个：foo.h需要bar.h中的定义，反之亦然。

Now, here is the problem - when writing the header files, each header depends on the other: foo.h needs the definitions in bar.h and vice-versa. What is the proper way of dealing with this?

推荐答案

您需要将所有成员访问权移出标题， 。

You need to move all of the member access out of the header, and into your source files.

这样，您可以在标题中转发声明的类，并在foo中定义它们：

This way, you can forward declare your classes in the header, and define them in foo:

// foo.h
class bar;

class foo {
    bar * m_pbar;
}

// bar.h
class foo;
class bar {
    foo * parent;
}

这将允许你工作 - 成员信息到您的头中 - 将其移动到.cpp文件。 .cpp文件可以包括foo.h和bar.h：

That will allow you to work - you just can't put definitions that require member information into your header - move it to the .cpp file. The .cpp files can include both foo.h and bar.h:

// Foo.cpp
#include "foo.h"
#Include "bar.h"

void foo::some_method() {
     this->m_pbar->do_something(); // Legal, now, since both headers have been included
}

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