Issue with classes

[Deimos]

Hey, Everyone.

I recently came across an issue regarding some classes having access to other classes' members. For instance, I have classes such as TextField, Button, Menu etc... and I have a master class Game. I want every instance of my other classes knowing their parent's location in memmory as to be able to access some of its members directly, something like this:

class Entity
{
    public:
        static std::vector<Entity*> entityList;
        static Game* game;

    private:

        {...}

    public:
        Entity();
        virtual ~Entity();

        {...}
};

Can I achieve this without having to include ALL of the Game.h header file?

Best Regards,
~Deimos

[Disch]

you could forward declare Game:

class Game;

class Entity
{
 //... 

Although -- this approach requires you to fill the 'game' pointer for every created object. If it's assumed there is only one global Game object, you can take a different approach.

// in game.h

class Game
{
  // ...
public:
  static Game& GetGame();  // return a reference to the global Game object
};

This way other objects can just call Game::GetGame() when they need to access the Game, and they don't need to own their own pointer to it. It's a little less flexible because it limits you to 1 Game, but is a bit easier to work with.

Any .cpp file that uses a Game pointer (like accesses any members or calls any functions, etc) will need to #include "game.h". There is no way around that.

[Deimos]

Ok, thanks a lot, Disch!
Since Game IS a singleton, it makes perfect sense to take the GetGame aproach! :D
Here's my code, any comments or sugestions appreciated!

//Game.h

class Game
{
    public:
        static Game *instance;

    private:
        {...}
    public:
        Game();
        ~Game();

        {...}
        static Game* getGame()  { assert(instance); return instance; }
};

//Game.cpp

#include "Game.h"

Game* Game::instance = NULL;

Game::Game()
{
    //kill app if there is more than one instance of Game
    assert(!instance);
    instance = this;

    {...}
}

Again, thank you and best regards
~Deimos

[Hammurabi]

Hiding the constructor forces the use of getGame().
You can also make the Game pointer private.

#include <iostream>

class Game
{
private:
    static Game* game;

    Game() {}           // Hide constructor

public:
    static Game* getGame()
    {
        if( ! game ) game = new Game;
        return game;
    }
    
    void isGameInited()
    {
        std::cout << std::boolalpha << (game != 0);
    }
};

Game* Game::game = 0;

int main()
{
    Game* game = Game::getGame();
    game->isGameInited();
}

[PanGalactic]

And you probably want to make the copy constructor and assignment operator private and unimplemented.