macOS NSNotificationCenter keeping my view controller from being deallocated?

[misee]

I have a document based application which uses QTMovieView to display a movie. The view in which the movie is displayed is hooked to MovieViewController (a subclass of NSViewController). At first, I used QTMovieViews default controls, but once everything was running, I decided to implement my own controls. To update the play/pause button, I added added the some code to

// Following method is called when a new path for the movie was set
- (void)handleMoviePathDidChange
{
    if (self.movie) //movie holds an instance of QTMovie
        [[NSNotificationCenter defaultCenter] removeObserver:self name:QTMovieRateDidChangeNotification object:self.movie];

    // "Old" code that didn't cause any trouble before
    NSError *error = nil;
    self.movie = [QTMovie movieWithURL:self.moviePath error:&error];
    if (error)
        [self handleError:error];
    
    [self.movieView setMovie:self.movie];
    // End of "old" code.
    
    if (self.movie)
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieRateChanged:) name:QTMovieRateDidChangeNotification object:self.movie];
}

Now, when I close the window, the MovieViewControllers dealloc is never called and the movie keeps playing (at least the sound - since the window is closed, I can't see it anymore). If I comment out the

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieRateChanged:) name:QTMovieRateDidChangeNotification object:self.movie];

and

[[NSNotificationCenter defaultCenter] removeObserver:self name:QTMovieRateDidChangeNotification object:self.movie];

calls, everything works as expected again, and dealloc is called.
I have tried registering for NSWindowWillCloseNotification and removing myself from there using

[[NSNotificationCenter defaultCenter] removeObserver:self]

but that didn't help either.
All other view controllers and the window controller are being deallocated as expected.
Any ideas on where the problem is?

 

[jiminaus]

You registered for NSWindowWillCloseNotification on an NSWindow object right? Because I can't see why that wouldn't have worked.

An alternative approach would be to make this class a delegate of the window and unregister in windowWillCloseNSNotification*).

 

[misee]

Yes, I registered on a window object like so:

- (void)awakeFromNib
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(windowWillClose:) name:NSWindowWillCloseNotification object:[self.view window]];
}

- (void)windowWillClose:(NSNotification *)notification
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

windowWillClose: is being called when I close the window, I already checked that. It seems weird, since I can't see why my calls to the notification center should increase my retain count/prevent the instance from getting deallocated.

 

[gnasher729]

Use NSLog to check whether the object that you add as an observer and the object that you remove as an observer are the same. I suspect one is some kind of controller and the other is some kind of window.

 

[misee]

Use NSLog to check whether the object that you add as an observer and the object that you remove as an observer are the same. I suspect one is some kind of controller and the other is some kind of window.

It's the same:

-[MovieViewController handleMoviePathDidChange] Add observer <MovieViewController: 0x100ddde60> for object <QTMovie: 0x7fcdd9bb2800 time scale = 600, duration = 3550544, rate = 0.000000, tracks = { 0x7fcdd9a7efd0 0x7fcdd9a7f060 }>
-[MovieViewController windowWillClose:] Remove observer <MovieViewController: 0x100ddde60>

Well, I did register self, so I guess it would have been unlikely that those two are different (I did hope it was that though).
Also, MovieViewController is instantiated in the document window nib file and is referenced nowhere else. I just searched my project for any occurrences of MovieViewController, but the only hits were in MovieViewController.[hm]. Target OS is 10.7 and I'm running it on 10.7.1.

 

[misee]

Problem solved.
To update the position, I used a timer. This is the way I did it:

- (void)movieRateChanged:(NSNotification *)notification
{
    // some code to update playing state

    if (self.updateTimer)
        [self.updateTimer invalidate];
    self.updateTimer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(updateTimerFired:) userInfo:nil repeats:YES];
}

I just went over the entire code again and saw it. I changed it to the following:

[self.updateTimer invalidate];
if (self.playing)
    self.updateTimer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(updateTimerFired:) userInfo:nil repeats:YES];
else
    self.updateTimer = nil;

Guess I suffered some kind of delusion when I wrote that code. Just goes to show: The problem is never where you actually look for it. Thanks for your time gnasher729 and jiminaus.