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POC++: circular dependency issue
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2013-05-07T13:24:11.453
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2013-05-07T13:26:38.490
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I'm having a problem with circular dependencies, I suppose this is a design flaw from introducing the Game class in the wrong way. Game.h: <pre><code>#pragma once #include <SFML\Graphics.hpp> #include "GameScreen.h" #include "TitleScreen.h" class Game { protected: sf::RenderWindow window; GameScreen* CurrentGameScreen; TitleScreen Title; public: Game(void); ~Game(void); sf::RenderWindow getWindow(void); void Run(); void Close(); }; </code></pre> GameScreen.h: <pre><code>#pragma once #include "Game.h" class GameScreen { public: GameScreen(void); ~GameScreen(void); virtual void LoadAllResources() {}; virtual void DrawScreen(Game* game) {}; virtual void Update(Game* game) {}; }; </code></pre> TitleScreen.h: <pre><code>#pragma once #include <SFML\Graphics.hpp> #include "GameScreen.h" class TitleScreen : public virtual GameScreen { private: sf::Texture title_screen; sf::Sprite titleScreen; sf::Font font; sf::Text menuExit; public: TitleScreen(void); ~TitleScreen(void); void LoadAllResources(); void DrawScreen(Game* game); void Update(Game* game); }; </code></pre> Then there's the main file: <pre><code>#include "Game.h" int main() { Game game; game.Run(); //sf::RenderWindow window(sf::VideoMode(800, 600), "Test"); //GameScreen* currentScreen; //TitleScreen titleScreen; //currentScreen = &titleScreen; //while (window.isOpen()) //{ // currentScreen->Update(&window); // currentScreen->DrawScreen(&window); //} return 0; } </code></pre> GameScreen.h and TitleScreen.h raise a handful of C2061. From what I understand these are caused by circular dependencies between Game.h and Gamescreen.h. TitleScreen.h is giving me error C2504: 'GameScreen' : base class undefined. Game.h: on lines 12 and 13, give C2143: syntax error : missing ';' before '*', although I'm not sure where this is coming from and my IDE is not giving me any syntax errors. If I remove the <code>#include</code> statement from GameScreen.h and substitute it with a forward declaration <code>class Game;</code> (which I guess breaks the circular dependency?) most of the above is solved, but TitleScreen.cpp throws a set of C2027, C2227 and C2228 (undefined type, left of -> and left of .) every time I try to access a Game object. IntelliSense points out that a pointer to an incomplete class is not allowed. I got it working before introducing the Game class - <code>DrawScreen()</code> and <code>Update()</code> would take as argument a pointer to window (<code>sf::RenderWindow* window</code>). There's part of the old code left in main.cpp.
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<c++><circular-dependency>
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C++: circular dependency issue
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1. COAs answered @piokuc, you need a [Forward declaration](http://en.wikipedia.org/wiki/Forward_declaration)
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