Handling Custom Property Observers in Objective-C for Dynamic UI Updates
I'm testing a new approach and I've searched everywhere and can't find a clear answer... I'm working on an iOS app where I need to dynamically update the UI based on changes to a custom object property. I have a `User` class with a `@property (nonatomic, strong) NSString *username;`. I'm using KVO (Key-Value Observing) to observe changes to this property, but I'm running into an scenario where the UI doesn't update as expected when the property changes. I've set up my observer like this in my `ViewController`: ```objective-c [self.user addObserver:self forKeyPath:@"username" options:NSKeyValueObservingOptionNew context:nil]; ``` However, in my `observeValueForKeyPath:ofObject:change:context:` method, I'm trying to update a UILabel with the new username: ```objective-c - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context { if ([keyPath isEqualToString:@"username"]) { self.usernameLabel.text = change[NSKeyValueChangeNewKey]; } } ``` The property updates correctly, but sometimes the UI doesn't refresh, and I see a warning in the console saying `-[__NSCFString length]: unrecognized selector sent to instance`. It seems to only happen after multiple updates, which makes me think there might be a memory management scenario or a timing question. I've tried adding `self.usernameLabel.text = [change[NSKeyValueChangeNewKey] copy];`, and I've verified that `self.usernameLabel` is not nil. I also tried removing the observer in `dealloc`, but I'm unsure if I'm missing something else. Does anyone have insights into why this might be happening or how to ensure the UILabel updates correctly every time the username changes? Am I missing something obvious? This is my first time working with Objective-C stable. Thanks for any help you can provide!