Best time to invalidate NSTimer inside UIViewController to avoid retain cycle

user_2198699 0
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Does any one know when is the best time to stop an NSTimer that is held reference inside of a UIViewController to avoid retain cycle between the timer and the controller?

Here is the question in more details: I have an NSTimer inside of a UIViewController.

During ViewDidLoad of the view controller, I start the timer:

statusTimer = [NSTimer scheduledTimerWithTimeInterval: 1 target: self selector: @selector(updateStatus) userInfo: nil repeats: YES];

The above causes the timer to hold a reference to the view controller.

Now I want to release my controller (parent controller releases it for example)

the question is: where can I put the call to [statusTimer invalidate] to force the timer to release the reference to the controller?

I tried putting it in ViewDidUnload, but that does not get fired until the view receives a memory warning, so not a good place. I tried dealloc, but dealloc will never get called as long as the timer is alive (chicken & egg problem).

Any good suggestions?

nstimer memory-leaks memory-management objective-c iphone
10 Answers

For @available(iOS 10.0, *) you could also use:

Timer.scheduledTimer(
    withTimeInterval: 1,
    repeats: true,
    block: { [weak self] _ in
        self?.updateStatus()
    }
)
user_39239290
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