Is it possible I have forward declaration of a class, without making them reference or pointer in header file

Question

// I prefer to perform forward declaration on myclass, as I do not
// wish to ship "myclass.h" to client
// However, the following code doesn't allow me to do so, as class defination
// is needed in header file.
//
// a.h
#include "myclass.h"
class a {
public:
    a();
    myclass me;
};

---

I try to do it another way around. However, I need to use dynamic allocation, which I usually try to avoid.

// a.h
class myclass;
class a {
public:
    a();
    myclass& me;
};

// But I just wish to avoid new and delete, is it possible?
// a.cpp
#include "myclass.h"

a::a() : me(*(new myclass())) {
}

a::~a() {
    delete *myclass;
}

Is it possible to do so, without using any reference or pointer? (Or more precisely, without using new/delete)

Answer 1

No. The reason being, that the compiler needs to know the size of your object (i.e. myclass) in order to know the size of the object (i.e. class "a" in your example). If you have only forward declared myclass, the compiler has no way of knowing the size that must be allocated for the "a" class.

A reference or pointer alleviates this b/c a pointer or reference has a defined size at the time of compilation and thus the compiler knows the memory requirements.