Thread: Mutual Classes

Hi I have the following problem. I have two classes and two header files. However, One class needs to use the other, and vice-versa. Now when I compile, because a has already been defined, when the preprocessor comes to class b, it will open up class a's header file find that a has already been defined (because the preprocessor did class a first), and therefore a's class definition will not get inserted into class b's header file. Then the compiler will throw an error will say a is undefined within class b. Which is correct. How do I get around this problem? If I got rid of the preprocessor commands I would probably get a class redefinition error... Code below is only illustration!

Code:

#ifndef a
#define a

#include "b.h"

Class a
{
  b *tmp;
}
#endif

#ifndef b
#define b

#include "a.h"

Class b
{
  a *tmp;
}
#endif

Any help would be appreciated. Additionally, if some of my thinking is slightly off regarding the actions of the preprocessor, please dont have a go.

So I wouldn't be able to seperate the two classes into two different files? Would both classes have to be declared within the same .h file?

So say in the header file for class a, what preprocessor command would I need to use so that the compiler knows of class b's existance, and that class a is going to be using class b?

Thats exactly what I needed, Thank you.

Hi, I tried using your first example, but got compiler errors, so I included the class defintion and implementation directly into my main cpp file. Though this time it says : "'b::test' uses undefined class 'a'"

Code:

#include <tchar.h>

class a;
class b;

class b
{
	a test;
	b(){};
};

class a
{
	b test;
	a(){};
};

int _tmain(int argc, _TCHAR* argv[])
{
	return 0;
}

Any ideas on how to get this working?

Your a legend cocker, got it working within my main project now instead of that test console one. Thanks for your help again. Dene