C ++循环包括 [英] C++ circular include

问题描述

我不能解决这个循环依赖问题;总是得到这个错误：
无效使用不完全类型struct GemsGame
我不知道为什么编译器不知道GemsGame的声明，即使我包括gemsgame.h
两者类依赖于彼此（GemsGame存储GemElements的向量，GemElements需要访问这个相同的向量）

I can't solve this circular dependency problem; always getting this error: "invalid use of incomplete type struct GemsGame" I don't know why the compiler doesn't know the declaration of GemsGame even if I included gemsgame.h Both classes depend on each other (GemsGame store a vector of GemElements, and GemElements need to access this same vector)

这里是GEMELEMENT.H的部分代码：

Here is partial code of GEMELEMENT.H:

#ifndef GEMELEMENT_H_INCLUDED
#define GEMELEMENT_H_INCLUDED

#include "GemsGame.h"

class GemsGame;

class GemElement {
    private:
        GemsGame* _gemsGame;

    public:
        GemElement{
            _gemsGame = application.getCurrentGame();
            _gemsGame->getGemsVector();
        }
};


#endif // GEMELEMENT_H_INCLUDED

... of GEMSGAME.H：

...and of GEMSGAME.H:

#ifndef GEMSGAME_H_INCLUDED
#define GEMSGAME_H_INCLUDED

#include "GemElement.h"

class GemsGame {
    private:
        vector< vector<GemElement*> > _gemsVector;

    public:
        GemsGame() {
            ...
        }

        vector< vector<GemElement*> > getGemsVector() {
            return _gemsVector;
        }
}

#endif // GEMSGAME_H_INCLUDED

推荐答案

删除 #include 指令，您已经向前声明了类。

Remove the #include directives, you already have the classes forward declared.

如果你的类A在它的定义中需要知道类B的细节，那么你需要包含类B的头部。如果A类只需要知道B类存在，例如当A类只保存一个指向B类实例的指针，那么它就足以转发声明，在这种情况下， #include 。

If your class A needs, in its definition, to know something about the particulars of class B, then you need to include class B's header. If class A only needs to know that class B exists, such as when class A only holds a pointer to class B instances, then it's enough to forward-declare, and in that case an #include is not needed.

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