Question

I’m currently trying to make a RPG game and I’m running into some trouble. This is the layout I have so far.

Classes:

• Actor – Base class for anything that ‘exists’ such as units, projectiles, etc.
• Unit – Inherits Actor, basis for all units.
• Game – It will only have a single instance, and it’ll contains pointers to all objects in the game. I plan to make it call a virtual function gameTick on all actors every 0.1 seconds.

The problem I’m having is that I’d like all Actors to have a pointer to the Game instance. If I wanted to have a spell that does 500 radius area damage, I’d like Game to find and return all Unit pointers within that range.

My problem is if I include Game in Actor’s header file my program won’t compile. How can I have my actors have access to Game? Or am I going about this the wrong way?

Thanks in advance.

// START main.cpp

#include <iostream>
#include "game.h"

int main()
{
    std::cout << "All done\n";

    return 0;
}

// END main.cpp



// START actor.h

#ifndef __ACTOR_H_
#define __ACTOR_H_

#include <iostream>

//#include "game.h" Causes many errors if uncommented

class Actor
{
public:
    Actor();

    std::string name_;
};

#endif

// END    actor.h



// START actor.cpp

#include "actor.h"

Actor::Actor()
{
    name_ = "Actor class";
}
// END actor.cpp



// START unit.h

#ifndef __UNIT_H_
#define __UNIT_H_

#include "actor.h"

class Unit : public Actor
{
public:
    Unit();
};

#endif

// END unit.h



// START unit.cpp

#include "unit.h"

Unit::Unit()
{
    name_ = "Unit class";
}

// END unit.cpp



// START game.h

#ifndef __GAME_H_
#define __GAME_H_

#include <vector>

#include "unit.h"

class Game
{
public:
    std::vector< Actor * > actors_;
    std::vector< Unit * > units_;
};

#endif

// END game.h

Answer 1

Instead of doing:

#include "actor.h"
#include "unit.h"

you can simply forward declare the two classes:

class Actor;
class Unit;

Since you’re only using pointers, the compiler just needs to know that the type is a class, it doesn’t need to know anything else. Now in the cpp file, you’d need to do the #includes