Hello, all ...
I'm experiencing weird issues with addObserver / removeObserver. I
log when I add observers, as well as when I try to remove them, but I
sometimes (not always) get an exception when I remove an observer:
2008-11-11 10:05:49.939 Magnatune[1382:20b] creating and starting
audio engine to play mp3 stream http://he3.magnatune.com/all/02-La%20Febre%20(Uccellini)-Altri%20Stromenti.mp3
2008-11-11 10:05:49.962 Magnatune[1382:20b] audio engine created --
streamer is 90fe00
2008-11-11 10:05:49.970 Magnatune[1382:20b] adding observers ... 11d3b0
2008-11-11 10:05:49.983 Magnatune[1382:ae93] AudioStreamer -
startInternal ...
2008-11-11 10:05:50.002 Magnatune[1382:20b] playing stream 1
2008-11-11 10:05:50.534 Magnatune[1382:20b] AudioStreamer -stop() called
2008-11-11 10:05:50.539 Magnatune[1382:20b] AudioStreamer -stop()
finished
... the crash:
2008-11-11 10:05:51.538 Magnatune[1382:20b] *** Terminating app due to
uncaught exception 'NSRangeException', reason: 'Cannot remove an
observer <MagnatuneAppDelegate 0x11d3b0> for the key path
"buffersEmpty" from <AudioStreamer 0x90fe00> because it is not
registered as an observer.'
The MagnatuneAppDelegate address (11d3b0) is the same, so i'm adding
observers to / removing observers from the same (and only) instance.
Why does Cocoa then think that I didn't add the "buffersEmpty"
observer when I clearly did?
The crash happens here, in the MagnatuneAppDelegate -stopStream method:
- (void)stopStream
{
if (streamer)
{
[streamer removeObserver:self forKeyPath:@"buffersEmpty"];
[streamer stop];
}
}
... and MagnatuneAppDelegate spawns the streamer thread like this:
- (void)playStream:(UInt32)streamIndexToPlay
{
NSLog(@"playStream -- current thread ID: %x", [NSThread
currentThread]);
.
.
.
if (streamIndexToPlay < [self countOfCurrentSongList])
{
self.donePlaying = false;
Song *streamToPlay = [self
objectInCurrentSongListAtIndex:streamIndexToPlay];
NSString *address = @"http://he3.magnatune.com/all/";;
address = [address stringByAppendingString:streamToPlay.mp3];
.
.
.
NSURL *url = [NSURL URLWithString:[address
stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding]];
NSLog(@"creating and starting audio engine to play mp3 stream %s",
[[url description] UTF8String]);
streamer = [[AudioStreamer alloc] initWithURL:url];
NSLog(@"audio engine created -- streamer is %x", streamer);
NSLog(@"adding observers ... %x", self);
[streamer addObserver:self forKeyPath:@"isPlaying" options:0
context:nil];
[streamer addObserver:self forKeyPath:@"failed" options:0
context:nil];
[streamer addObserver:self forKeyPath:@"buffersEmpty" options:0
context:nil];
[streamer start];
}
.
.
.
}
The AudioStreamer -start method is:
- (void)start
{
streamerThread = [[NSThread alloc] initWithTarget:self
selector:@selector(startInternal) object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(threadStopped)
name:NSThreadWillExitNotification
object:streamerThread];
[streamerThread start];
MagnatuneAppDelegate *appDelegate = (MagnatuneAppDelegate *)
[[UIApplication sharedApplication] delegate];
appDelegate.playbackThreadFinished = false;
}
Regards,
John
Falling You - exploring the beauty of voice and sound
http://www.fallingyou.com
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