NSTimer disables dealloc in UIView

Question

@interface someview:UIView{
  NSTimer* timer;
}
@end

@implementation someview

-(void)dealloc{
  NSLog(@\"dealloc someview\");
  [timer invalidate];
  timer = nil;
}
-(         


        

Answer 1

As mentioned above, Timers retain their targets. Until the timer is invalidated, there is a retain cycle between the timer and the view, so the view will not be deallocated.

I would invalidate the timer when it's removed from the view hierarchy by subclassing didMoveToSuperview, this gets called by the system when there is a View-Related Change (e.g superview changes). The 'removeFromSuperview' is only called when removeFromSuperview is called on UIView

- (void)didMoveToSuperview
{
    [super didMoveToSuperview];

    if (!self.superview)
    {
        [timer invalidate];
        timer = nil;
    }
}

Answer 2

NSTimer retains the target. Therefore, the timer must be invalidated before your view is dealloc'd.

Answer 3

I think the best solution when using an NSTimer inside of a UIView is to override the removeFromSuperview method;

- (void)removeFromSuperview
{
    [timer invalidate];
    timer = nil;

    [super removeFromSuperview];
}

The only thing to keep in mind here is that you need to ensure that timer is not a nil object because removeFromSuperview can also get automatically called from other UIView's super dealloc methods. You could wrap in a conditional to check.