nsnotification

Basically, I have a view1 which at some point, calls view2 (via presentModalViewController:animated: ). When a certain UIButton in view2 is pressed, view2 is calls a notification method in view1 and immediately afterward is dismissed. The notification method pops up an alert. The notification method works fine and is called appropriately. The problem is, every time view1 is created (only one view1 should exist at a time), I presumably get another NSNotification being created because if I go from view0 (the menu) to view1, then back and forth a few times, I get a series of the same alert

I would like to call a method that takes an NSNotification immediately after the user presses the camera shutter (i.e when the "Preview" tab bar has the buttons "Retake" and "Use"). I can't use the didFinishPickingImage method because at this time the user has already pressed the "Use" button. I have already implemented this by cameraOverlayView property of UIImagePickerController(see comments), but I wonder whether there are quicker ways of 'observing' this action. Any ideas? Axel To learn about camera button press event, you can fire a NSNotification for it. // Add observer for when camera

I have this code below which runs when the keyboardWillShowNotification is called: func keyboardWillShow(_ notification: Notification) { //ERROR IN THE LINE BELOW keyboard = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as AnyObject).cgRectValue animaton = (notification.userInfo?[UIKeyboardAnimationDurationUserInfoKey] as AnyObject).doubleValue UIView.animate(withDuration: 0.4, animations: { () -> Void in self.scrollView.frame.size.height = self.scrollViewHeight - self.keyboard.height }) } I am getting an error on the second line saying: unexpectedly found nil while unwrapping an

I need to create two classes and both should be able to send and receive the events through the NSNotificationCenter methods.ie Both should have the sendEvent and receiveEvent methods: @implementation Class A -(void)sendEvent { addObserver:--- name:---- object:--- } -(void)ReceiveEvent { postNotificationName: --- object:--- } @end Same as such another class say ClassB should also be able to send and receive the events. How can it be done? Ideally an object would start observing interesting events as soon as its initialized. So it will register all interesting events with the NotificationCenter

In Objective-C, a custom notification is just a plain NSString, but it's not obvious in the WWDC version of Swift 3 just what it should be. You could also use a protocol for this protocol NotificationName { var name: Notification.Name { get } } extension RawRepresentable where RawValue == String, Self: NotificationName { var name: Notification.Name { get { return Notification.Name(self.rawValue) } } } And then define your notification names as an enum anywhere you want. For example: class MyClass { enum Notifications: String, NotificationName { case myNotification } } And use it like