Question

I just decided to run a test upon suspecting some behavior:

In my view controller I have a new game method which does this:

-(void) newClassicGame {

    if (classicGame!=nil) {
        [classicGame saveStats];
    }

    classicGameController = nil;
    classicGameController = [[RegularGameViewController alloc] initWithPowerMode:NO ];

    classicGame = nil;
    classicGame = [[RegularGame alloc] initWithViewController:classicGameController];

    classicGameController.game = classicGame; // game property is __weak to avoid 
    //retain cycles.

    [classicGame startGame];

}

and to test if objects get destroyed with ARC, in the startGame method of classicGame, I put this:

-(void) startGame
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSLog(@"once");
        [NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(repeat) userInfo:nil repeats:YES];
    });
//other stuff..

}

-(void) repeat {

    NSLog(@"I repeat");

}

for those who are not familiar with dispatch_once method, it’s just a method that makes sure that the block gets called exactly once, and no more, during the life time of an application.

I start my app, hit new game and game starts – I see the log “I repeat” repeating every 3 seconds”.. Then I go back to the menu and hit new game again. Strangely, the log keeps on repeating, indicating that my classicGame instance is not completely destroyed and the timer is still running somewhere. Any ideas what is happening here?

Answer 1

The timer that you create retains its target (self, the game), so your game object won’t be deallocated at least until the timer is invalidated.