Untitled

forward declaration in another file c
#ifndef _MAIN_H_
#define _MAIN_H_
class ClassA;
class ClassB;
#include "classa.h"
#include "classb.h"
#endif

#ifndef _CLASSA_H_
#define _CLASSA_H_
#include "main.h"
class ClassA
{
public:
    ClassB b;
};
#endif

#ifndef _CLASSB_H_
#define _CLASSB_H_
#include "main.h"
class ClassB
{
public:
    ClassA a;
};
#endif

#pragma once
class ClassB;
class ClassA
{
public:
    ClassB* b;
}

#pragma once
#include "ClassA.h"
class ClassB
{
public:
    ClassA a;
}