addobserver

To my understanding the object parameter of the addObserver method is the object you want to receive notifications from. Most of the time I see it as nil (I assume this is because notifications of the specified type are wanted from all objects). In my particular case I have a text field at the top of the screen and at the bottom of the screen and I want the view to move up only when the user taps the bottom text field, not the top one. So I call the following method in viewWillAppear func subscribeToKeyboardNotifications() { NSNotificationCenter.defaultCenter().addObserver(self, selector:

Is it possible to add observers to simple variables such as BOOLs or NSIntegers and see when they change? Thanks! You observe keys to be notified when their value changes. The data type can be anything. For anything defined as an Objective-C property (with @property in the .h file) this is ready to go so if you want to observe a BOOL property you add to a view controller you do it as follows: in myViewController.h: @interface myViewController : UIViewController { BOOL mySetting; } @property (nonatomic) BOOL mySetting; in myViewController.m @implementation myViewController @synthesize mySetting

Looking at various Apple examples (for example Add Music ) in which I see they add observers to the default NSNotificationCenter in viewDidLoad , then remove them in dealloc . This seems dangerous as viewDidLoad can be called multiple times without dealloc being called. This would then add the same observer multiple times, causing the handler to be called multiple times. A solution to this would be to also remove observers in viewDidUnload , but this would then mean the same observer could be removed for a second time in dealloc which seems like a potential problem. What am I missing? Lorenzo

I couldn't find an easy way to update the view in my iPhone app when I push a button on the AppleWatch App yet. I tried it with NSUserDefaults Observer like this: iPhone App Viewcontroller(inside ViewDidLoad()): // Create and share access to an NSUserDefaults object. mySharedDefaults = NSUserDefaults(suiteName: "group.sharedTest") //Add Observer NSUserDefaults.standardUserDefaults().addObserver(self, forKeyPath: "test", options: NSKeyValueObservingOptions.New, context: nil) In the Watchkit Extensions InterfaceController I added an IBAction with the button with this code: mySharedDefaults!