Question

I’ve looked around for a while, tried quite a few different approaches to this issue, but still cannot seem to get past errors occurring from forward declaration in a program with 3 codependent classes.

Here’s a abstracted view of my current code’s structure, split into 6 files + 1 main program file:

File x.h:

#ifndef X_H
#define X_H

using namespace std;

class y;

class x
{
    private:
        y *m_oY;
    public:
        // constructors &c
};
#endif

File x.cpp:

#include "x.h"
#include "y.h"
// Fancy stuff...

File y.h:

#ifndef Y_H
#define Y_H

using namespace std;

class z;

class y
{
    private:
        z *m_oZ;
    public:
        // constructors &c
        z *funcZ()
};
#endif

File y.cpp:

#include "y.h"
#include "z.h"
// Fancy stuff...

File z.h:

#ifndef Z_H
#define Z_H

using namespace std;

class z { ... };
#endif

File z.cpp:

#include "z.h"
// Fancy stuff...

File main.cpp:

#include "z.h"
#include "y.h"
#include "x.h"
#include <iostream>

using namespace std;

int main() { ... }

The first error I receive, trying to compile in VS with a clean, non-PCH, non-ATL project occurs in my implementation when trying to use Class z. The error tells me that it’s using the definition of z from y.h, and I’m not sure how to remedy this without creating a circular include problem. Text of the error follows:

main.cpp(114) : error C2514: ‘z’ : class has no constructors

y.h(9) : see declaration of ‘z’

Any clues as to what I’m doing wrong here?

Answer 1

This isn’t a forward declaration problem. Main.c can see the full declaration of class z. It must be that z has no constructor, at least of the proper shape, or maybe it is private.