「交換」一個UIView實例變量 - 不能dealloc「先前」視圖

Question

我想組織某種程度上我的iPhone遊戲的水平視圖，但我根本無法（沒有展開對象分配）。我做了一個真正的「骨架」我的代碼（這個遊戲有2個關卡，目標是發佈iPhone顯示屏）。我不能釋放前一級，因此Instrunments會顯示增加BGTangramLevel實例。

請看看它，我需要一些有用的想法設計（我的第三個問題）。

viewcontroller.h

@interface compactTangramViewController : UIViewController 
{ 
    //The level. 
    BGTangramLevel *currentLevel; 
    UIColor *levelColor; 
} 

//It is to be just a reference, therefore I use assign here. 
@property (nonatomic, retain) BGTangramLevel *currentLevel; 

-(void) notificationHandler: (NSNotification*) notification; 
-(void) finishedCurrentLevel; 

@end 

viewcontroller.m

@implementation compactTangramViewController 
@synthesize currentLevel; 

//Initializer functions, setting up view hierarchy. 
-(void) viewDidLoad 
{ 

    //Set up levelstepper. 
    levelColor = [UIColor greenColor]; 

    //Set up "state" classes. 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(notificationHandler:) name:@"finishedCurrentLevel" object:nil]; 

    //Attach level 1. 
    currentLevel = [BGTangramLevel levelWithColor: levelColor frame:self.view.frame]; 
    [self.view addSubview:currentLevel]; 

    [super viewDidLoad]; 

} 

//Release objects. 
-(void) dealloc 
{ 
    [currentLevel release]; 
    [super dealloc]; 
} 

//Notification handling. 
-(void) notificationHandler: (NSNotification*) notification 
{ 
    //Execute level swap. 
    if ([notification name] == @"finishedCurrentLevel") [self finishedCurrentLevel]; 
} 

-(void) finishedCurrentLevel 
{ 
    //Remove previous level. 
    [currentLevel removeFromSuperview]; 
    //[currentLevel release]; 

    //Step level. 
    if (levelColor == [UIColor greenColor]) levelColor = [UIColor blueColor]; else levelColor = [UIColor greenColor]; 

    //Attach level 2. 
    currentLevel = [BGTangramLevel levelWithColor: levelColor frame:self.view.frame]; 
    [self.view addSubview:currentLevel]; 

} 
@end 

BGTangramLevel.h

@interface BGTangramLevel : UIView 
{ 
    BOOL puzzleCompleted; 
} 

//Initializer. 
+(BGTangramLevel*)levelWithColor: (UIColor*) color frame: (CGRect) frame; 

//Test if the puzzle is completed. 
-(void) isSolved; 

@end 

BGTangramLevel.m

@implementation BGTangramLevel 

//Allocated instance. 
+(BGTangramLevel*)levelWithColor: (UIColor*) color frame: (CGRect) frame 
{ 
    BGTangramLevel *allocatedLevel = [[BGTangramLevel alloc] initWithFrame:frame]; 
    allocatedLevel.backgroundColor = color; 
    return allocatedLevel; 
} 

//Finger released. 
-(void) touchesEnded: (NSSet*)touches withEvent: (UIEvent*)event 
{ 
    //The completement condition is a simple released tap for now... 
    puzzleCompleted = YES; 
    [self isSolved];  
} 

//Test if the puzzle is completed. 
-(void) isSolved 
{ 
    //"Notify" viewController if puzzle has solved. 
    if (puzzleCompleted) [[NSNotificationCenter defaultCenter] postNotificationName:@"finishedCurrentLevel" object:nil]; 
} 

-(void) dealloc 
{ 
    NSLog(@"Will ever level dealloc invoked."); //It is not. 
    [super dealloc]; 
} 

@end 

那麼我該怎麼做？我嘗試標記autorelease返回的級別實例，在removeFromSuperview後釋放currentLevel，嘗試以（非原子，分配）方式合成的currentLevel屬性，但Object Allocations仍在增長。我可以避免通知嗎？我卡住了。

Answer 1

您需要更緊密地遵循保留/釋放規則。你絕對不應該在實驗上添加保留，釋放和自動釋放，只是爲了找到有用的東西。已經有很多關於Cocoa內存管理的文章，我不會在這裏重複。

具體來說，BGTangramLevel的levelWithColor:frame:方法在返回其調用者之前應該調用[allocatedLevel autorelease]。它不擁有該對象，取決於調用者。

您還需要知道訪問實例變量和訪問屬性之間的區別。可可的屬性只是用於吸氣和吸氣方法的語法糖。當您在視圖控制器中引用currentLevel時，您正在直接處理實例變量。當你參考self.currentLevel你正在處理財產。

即使您已聲明屬性，currentLevel = [BGTangram ...]只是將引用複製到變量中。在viewDidLoad中，如果您想要通過屬性的setter方法，您將需要使用self.currentLevel = [BGTangram ...]，該方法將保留該對象（因爲您以這種方式聲明屬性）。看到不同？

我認爲你的泄漏發生在finishedCurrentLevel。如果您使用過self.currentLevel = [BGTangram ...]，則會調用該屬性的setter方法，該方法將釋放舊對象並保留新對象。由於您直接分配給實例變量，因此只需將舊引用覆蓋而不釋放它。

在您的視圖控制器的dealloc方法中調用[currentLevel release]是正確的。