Question

我有一个继承自CCSprite GameObject的类。我还有一个名为ActionDispatcher的单例，它继承自NSObject。

ActionDispatcher sharedActionDispatcher's作业是在被询问时返回CCActionInterval，执行此操作的方法需要引用询问对象，类型为GameObject（或其子类））。但是，GameObject能够提出要求，需要参考ActionDispatcher。我在#import "GameObject.h"标题中有一个ActionDispatcher，在#import "ActionDispatcher"标题中有一个GameObject。

我在Expected ')' before 'GameObject'方法中收到错误ActionManager，其中引用了GameObject。

编辑：添加评论以显示我根据下面接受的答案修正了这个问题。

//The GameObject interface

#import "cocos2d.h"
#import "ActionDispatcher.h"

@interface GameObject : CCSprite {
    CGPoint homeLocation;
}

@property (readwrite) CGPoint homeLocation;

- (void)updateStateWithDeltaTime:(ccTime)deltaTime 
        andListOfGameObjects:(CCArray*)listOfGameObjects;

@end

//The GameObject implementation

#import "GameObject.h"

@implementation GameObject

@synthesize homeLocation;

- (void)updateStateWithDeltaTime:(ccTime)deltaTime 
        andListOfGameObjects:(CCArray *)listOfGameObjects 
{
    //CCLOG(@"updateStateWithDeltaTime method should be overriden");
}

@end

//The ActionDispatcher interface

#import "cocos2d.h"
#import "CCRotateAround.h"
#import "Constants.h"
#import "GameObject.h" // Answer: Remove this line

// Add this here: @class GameObject;

@interface ActionDispatcher : NSObject {

}

+ (ActionDispatcher *)sharedActionDispatcher;

- (id)actionWithType:(ActionType)actionType 
          withObject:(GameObject *)gameObject 
        withDuration:(float)duration;

@end

//The ActionDispatcher implementation

#import "ActionDispatcher.h"
// and add this here: #import "GameObject.h"

@implementation ActionDispatcher

static ActionDispatcher* _sharedActionDispatcher = nil;

+ (ActionDispatcher*)sharedActionDispatcher 
{
    @synchronized([ActionDispatcher class])                             
    {
        if(!_sharedActionDispatcher)                                    
            [[self alloc] init]; 
        return _sharedActionDispatcher;                                 
    }
    return nil; 
}

+ (id)alloc 
{
    @synchronized ([ActionDispatcher class])                            
    {
        NSAssert(_sharedActionDispatcher == nil,
                 @"Attempted to allocated a second instance of the ActionManager singleton");                                          
        _sharedActionDispatcher = [super alloc];
        return _sharedActionDispatcher;                                 
    }
    return nil;  
}

- (id)actionWithType:(ActionType)actionType 
          withObject:(GameObject *)gameObject 
        withDuration:(float)duration
{
    CGSize screenSize = [[CCDirector sharedDirector] winSize];

    id action = nil;

    switch (actionType) {
        case kActionDiveBomb:
            CCLOG(@"ActionManager returning action of type: dive bomb");
            CGPoint controlPoint1 = ccp(gameObject.position.x, gameObject.position.y*0.5f);
            CGPoint controlPoint2 = ccp(screenSize.width*0.5f, gameObject.position.y*0.5f);
            CGPoint destination = ccp(screenSize.width*0.5f, -gameObject.contentSize.height*0.5f);
            ccBezierConfig diveBombBezier;
            diveBombBezier.controlPoint_1 = controlPoint1;
            diveBombBezier.controlPoint_2 = controlPoint2;
            diveBombBezier.endPosition = destination;
            id diveAction = [CCBezierTo actionWithDuration:duration bezier:diveBombBezier];
            id returnToTopAction = [CCMoveTo actionWithDuration:0.0f position:ccp(gameObject.homeLocation.x, screenSize.height+gameObject.contentSize.height/2)];
            id fallInAction = [CCMoveTo actionWithDuration:duration*0.2 position:gameObject.homeLocation];
            action = [CCSequence actions:diveAction, returnToTopAction, fallInAction, nil];
            break;
        case kActionLoop:
            CCLOG(@"ActionManager returning action of type: loop");
            CGPoint centerPoint = ccp(screenSize.width/2, screenSize.height/2);
            float span = 360.0;
            action = [CCRotateAround actionWithDuration:duration centerPoint:centerPoint spanAngle:span];
            break;
        case kActionSpin:
            CCLOG(@"ActionManager returning action of type: spin");
            action = [CCRotateBy actionWithDuration:duration angle:360.0f];
            break;
        case kActionGoHome:
            CCLOG(@"ActionManager returning action of type: go home");
            action = [CCMoveTo actionWithDuration:0.0f position:[gameObject homeLocation]];
            break;
        case kActionFallIn:
            CCLOG(@"ActionManager returning action of type: fall in");
            action = [CCMoveTo actionWithDuration:duration position:[gameObject homeLocation]];
            break;
        case kActionIdle:
            CCLOG(@"ActionManager returning action of type: idle");
            action = [CCDelayTime actionWithDuration:duration];
            break;
        default:
            CCLOG(@"ActionManager returning action of type: no valid action");
            break;
    }

    return action;
}

@end

Answer 1

只需在@class上方的ActionDispatcher.h中添加@interface指令即可。这是在实现中导入的类的前向声明。

@class GameObject;

Answer 2

可能的。尝试插入

@class GameObject

在ActionManager.m导入后

转发声明？这应该会打破这个循环。

Answer 3

这不是问题。 #import指令自动处理已包含文件的包含。 Discussion is here。要检查它注释掉所有其他导入，从NSObject继承您的GameObject，它将编译没有错误。该错误告诉您包含的其中一个文件有问题。有时它在@end关键字后的头文件中可能是一个错误的符号，这会使编译器在错误的地方抱怨。

这是循环参考吗？

3 个答案: