Do I set properties to nil in dealloc when using ARC?

Question

I am trying to learn Automatic Reference Counting in iOS 5. Now the first part of this question should be easy:

1. Is it correct that I do NOT

Answer 1

Just to give the opposite answer...

Short answer: no, you don't have to nil out auto-synthesized properties in dealloc under ARC. And you don't have to use the setter for those in init.

Long answer: You should nil out custom-synthesized properties in dealloc, even under ARC. And you should use the setter for those in init.

The point is your custom-synthesized properties should be safe and symmetrical regarding nullification.

A possible setter for a timer:

-(void)setTimer:(NSTimer *)timer
{
    if (timer == _timer)
        return;

    [timer retain];
    [_timer invalidate];
    [_timer release];
    _timer = timer;
    [_timer fire];
}

A possible setter for a scrollview, tableview, webview, textfield, ...:

-(void)setScrollView:(UIScrollView *)scrollView
{
    if (scrollView == _scrollView)
        return;

    [scrollView retain];
    [_scrollView setDelegate:nil];
    [_scrollView release];
    _scrollView = scrollView;
    [_scrollView setDelegate:self];
}

A possible setter for a KVO property:

-(void)setButton:(UIButton *)button
{
    if (button == _button)
        return;

    [button retain];
    [_button removeObserver:self forKeyPath:@"tintColor"];
    [_button release];
    _button = button;
    [_button addObserver:self forKeyPath:@"tintColor" options:(NSKeyValueObservingOptions)0 context:NULL];
}

Then you don't have to duplicate any code for dealloc, didReceiveMemoryWarning, viewDidUnload, ... and your property can safely be made public. If you were worried about nil out properties in dealloc, then it might be time you check again your setters.