Cross reference and circular dependency. Header including itself indirectly

Question

placeable.h

#include "selectable.h"

class placeable : selectable
{
..
};

selectable.h

#include "game.h"


class selectable
{
..
};

game.h

#include "placeable.h"

class game
{
...
class placeable* holding;
...
};

Basically placeable.h includes selectable.h which includes game.h which includes placeable.h again.

The only solution i can think of is placing the placeable* in a new header, making it static/global and then include this new header in game.h and selectable.h.

I'm sorry i dint include header guards in the upper code. I assumed it was obvious. Header guards does not help in this case because of the inheritance, same thing goes with forward declaring.

Answer 1

Only include headers if you MUST

Use forward declaration in preference to including:

You only need to include the header for class X iff:

• You have a member of the class 'X'
• You derive from the class 'X'
• You pass a parameter of class 'X' by value.

Otherwise a forward declaration will suffice.

//  -> Don't do this #include "placeable.h"
class     placeable;  // forward declare
                      // Fine if you are using a pointer.

class game
{
    ...
    class placeable* holding;
    ...
};

PS. Add header guards.