C ++循环标头包括 [英] C++ circular header includes
问题描述
我知道之前也曾问过类似的问题,但是在进行研究之后,我仍然对循环标题包含问题。
I know that similar questions to this have been asked before but after doing my research I still have questions about circular header includes.
//FooA.h
#ifndef H_FOOA
#define H_FOOA
#include "foob.h"
class FooA{
public:
FooB *fooB;
};
//FooB.h
#ifndef H_FOOB
#define H_FOOB
class FooA;
class FooB{
public:
FooA *fooA;
};
现在,如果我有两个循环依赖项,这就是我看到Stackoverflow上的人绕过问题。我唯一的问题是在我的main.cpp中,必须先包含fooa.h,然后再包含foob.h
Now if I have two circular dependencies this is the way that I have seen people on stackoverflow get around the problem. My only problem with this is that in my main.cpp I must include fooa.h first and then foob.h
//main.cpp the right way
#include "fooa.h"
#include "foob.h"
//main.cpp that will surely get a compile error
#include "foob.h"
#include "fooa.h"
现在我的问题是是否有一种方法可以转发声明这些类,从而使我不必关心在main.cpp中包含头文件的顺序?
Now my question is "Is there a way to forward declare these classes in a way that will allow me to not care about the order in which I include the header files in my main.cpp?"
推荐答案
是否可以通过一种方式转发声明这些类,从而使我不必关心标题的顺序我的main.cpp中的文件?
Is there a way to forward declare these classes in a way that will allow me to not care about the order in which I include the header files in my main.cpp?
由于您仅在处理简单指针,因此在两种情况下都可以在此处使用前向声明:
since you are dealing with simple pointers only, you can use a forward declaration here in both cases:
FooA.h
#ifndef H_FOOA
#define H_FOOA
// #include "foob.h" << not needed!
class FooB; // << substitute with a forward declaration of FooB
class FooA{
public:
FooB *fooB;
};
#endif
FooB.h
#ifndef H_FOOB
#define H_FOOB
class FooA;
class FooB{
public:
FooA *fooA;
};
#endif
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