Debugging Key-Value-Observing overflow.
- by Paperflyer
I wrote an audio player. Recently I started refactored some of the communication flow to make it fully MVC-compliant. Now it crashes, which in itself is not surprising.
However, it crashes after a few seconds inside the Cocoa key-value-observing routines with a HUGE stack trace of recursive calls to NSKeyValueNotifyObserver. Obviously, it is recursively observing a value and thus overflowing the NSArray that holds pending notifications.
According to the stack trace, the program loops from observeValueForKeyPath to setMyValue and back. Here is the according code:
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context {
if ([keyPath isEqual:@"myValue"] && object == myModel
&& [self myValue] != [myModel myValue]) {
[self setMyValue:[myModel myValue];
}
}
and
- (void)setMyValue:(float)value {
myValue = value;
[myModel setMyValue:value];
}
myModel changes myValue every 0.05 seconds and if I log the calls to these two functions, they get called only every 0.05 seconds just as they should be, so this is working properly.
The stack trace looks like this:
-[MyDocument observeValueForKeyPath:ofObject:change:context:]
NSKeyValueNotifyObserver
NSKeyValueDidChange
-[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:]
-[MyDocument setMyValue:]
_NSSetFloatValueAndNotify
…repeated some ~8k times until crash
Do you have any idea why I could still be spamming the KVO queue?
