[RESOLVED] Problems with classes (C2061)

[D_Drmmr]

The main problem (C2061) remains, though.

You have to include wall.h in ball.h

// wall.h

#ifndef WALL_H
#define WALL_H

class Wall
{
//...
};

#endif // WALL_H

// ball.h

#ifndef BALL_H
#define BALL_H

#include "wall.h"

class Ball
{
//...
    void foo(Wall& wall);
};

#endif // BALL_H