Possible circular reference problem

问题:

I am not an idiot, but header files make me feel like one sometimes. I have what is probably an overly-complicated set-up that has an error that I cannot resolve. Here it is in about as simple as detail as I can make it....

• I have a Controller class that contains a Model class.
• I have a Scene class to capture actions and communicates with the Controller.
• I have a Layer class that talks with the Model class to output the state of the Model.
• The Scene class contains Layer class solely for output.
• Scenes must hold Layers as determined by the Cocos2D framework.
• Specific Scene classes derive from a RootScene class that holds the reference to the Controller class.
• Specific Layer classes derive from a RootLayer class that holds the reference to the Model class.
• The Controller is responsible for creating Scenes and Scenes are responsible for creating Layers.

The problem comes when making a Layer and passing the Controller's Model to the Layer's Model (in AScene.m). I get the "Request for member 'Model' in something not a stucture or union". Casting doesn't work, and I'm at a loss for how to allow these classes to talk with each other. I think part of the problem might be that Controller class contains the Model class.

Controller.h

#import <Foundation/Foundation.h>

@class Model;
@class AScene;

@interface Controller : NSObject {
    Model *Model;
}
@property (nonatomic, retain) Model *Model;
-(void)runScene;

Controller.m

#import "Controller.h"

#import "Model.h"
#import "AScene.h"

@implementation Controller

@synthesize Model;

- (void)runScene {
    AScene *newScene = [[AScene alloc] init];
    newScene.controller = self;
}

RootScene.h

#import "cocos2d.h"

@class Controller;

@interface RootScene : Scene {
    Controller *controller;
}
@property (nonatomic, retain) Controller *controller;

@end

RootScene.m

#import "RootScene.h"
#import "Controller.h"

@implementation RootScene

@synthesize controller;

- (id) init {
    self = [super init];
    if (self != nil) {
        //
    }
    return self;
}

- (void) dealloc {
    [controller release];
    [super dealloc];
}

@end

AScene.h

#import "RootScene.h"

@class ALayer;
@class Model;

@interface AScene : RootScene {
}

@end

AScene.m

#import "AScene.h"
#import "ALayer.h"
#import "Model.h"

@implementation AScene

- (id) init {
    self = [super init];
    if (self != nil) {
        ALayer *newLayer = [ALayer node];
        newLayer.model = controller.Model; // <-- Request for member 'Model' in something not a stucture or union
        [self addChild:statusScreenLayer];
    }
    return self;
}

- (void) dealloc {
    [super dealloc];
}

@end

RootLayer.h

#import "cocos2d.h"

@class Model;

@interface RootLayer : Layer {
    Model *model;
}
@property (nonatomic, retain) Model *model;

@end

RootLayer.m

#import "RootLayer.h"

#import "Model.h"

@implementation RootLayer

@synthesize model;

- (id) init {
    self = [super init];
    if (self != nil) {
        //
    }
    return self;
}

- (void) dealloc {
    [model release];
    [super dealloc];
}

@end

ALayer.h

#import "RootLayer.h"

@interface ALayer : RootLayer {
}
-(void) draw;

@end

ALayer.m

#import "ALayer.h"

@implementation ALayer

-(void) draw {
    // draw based on state of the model
}

@end

回答1:

Your implementation of AScene does not #import the header of Controller.

Edit: Explicit solution.

In AScene.m add:

#import "Controller.h"

回答2:

Nikolai seems to be right. Beyond that, best practice would dictate that properties (like ivars) should NOT start with an uppercase letter. You're just asking for hurt. Use these instead:

Controller.h

@interface Controller : NSObject {
    Model *model;
}
@property (nonatomic, retain) Model *model;

Controller.m

@synthesize model;