"Attempting to use the forward class 'Game' as superclass of 'MathGame'" in Cocos2d

You simply have an import cycle:

1. Game imports SplashScreenLayer
2. SplashScreenLayer imports MathGame
3. MathGame imports Game

Your solution:

Leave the import inside the MathGame, and change the other imports to @class.

To sum it up:

// Game.h#import "cocos2d.h"#import <GameKit/GameKit.h>@class SplashScreenLayer;@interface Game : CCLayer    // A bunch of stuff@endThe new game type:// MathGame.h#import "Game.h"@interface MathGame : Game@endAnd the main menu that includes both:// SplashScreen.h#import "cocos2d.h"#import "HowToPlayLayer.h"#import "AboutLayer.h"@class Game;@class MathGame;@interface SplashScreenLayer : CCLayer    // A bunch of stuff@end

With your question answered above, let me explain a few things I already know from reading about forward declerations and import cycles:

First, go read about them! They are a very important part of Objective-C, and you don't want to miss it!

Secondly, use @class whenever you need that class for private variables or method parameters. Use imports for inheritance and strong properties.

Thirdly, don't forget to #import your forwarded classes in the implementation file!

In my case,I user the xx class and use the @class but not #import the .h file.and the compile complain..