observing a view's frame change

observe.M

// create the observer
[[self contentView] addObserver:self forKeyPath:@"frame" options:NSKeyValueObservingOptionNew context:NULL];


// track changes
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    
    if ([object isKindOfClass:[UIView class]]) {
        
        CGRect rect = [[change valueForKey:NSKeyValueChangeNewKey] CGRectValue];
        NSLog(@"changed rect: %@", NSStringFromCGRect(rect));
        
        // Cell * cell = (Cell*)[self.tableView cellForRowAtIndexPath:self.activeIndexDelete];
    }
    
}


// removing observer
@try{
  [[self contentView] removeObserver:self forKeyPath:@"frame"];
}
@catch (id exception) {
  // do something 
}