How does viewwillappear get called

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Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Now live: A fully responsive profile. Related Hot Network Questions. Question feed. If you layout out UIs with the appropriate autoresizing masks on the various bits, sometimes you don't even need to deal with the 'manual' laying out of your UI - it just gets dealt with No delegates or methods or delegate methods get called after that, since the being-killed app is probably in a really bad state and whatever data you might want to write out could be corrupted and non-usable.

If you use angular. What is happening is that angular is still watching the original p reference even after you do the assignment. This issue is resolved by checking the class of the destination view controller before trying to access one of its properties:. Problem finally solved.

I'm not sure what exactly caused the issue Masonry [constraints framework] or iOS8 changes to UILabel , but the solution was to change the view hierarchy. This is a great place to hide the keyboard, save state, and possibly cancel running timers or network requests. Like the other methods in the view controller lifecycle, be sure to call super at some point in viewWillDisappear.

Enter your name and email and start learning Swift today. If your app targets iOS 9. Use Notification Center in the viewDidLoad: method of your ViewController to call a method and from there do what you were supposed to do in your viewWillAppear: method. Calling viewWillAppear: directly is not a good option. That method is only invoked according to the relationship between the view controller's view and the application's window , i. When your application goes background, obviously the topmost views of the application window are no longer visible to the user.

In your application window's perspective, however, they are still the topmost views and therefore they did not disappear from the window. Rather, those views disappeared because the application window disappeared. They did not disappeared because they disappeared from the window.

Therefore, when the user switches back to your application, they obviously seem to appear on the screen, because the window appears again. But from the window's perspective, they haven't disappeared at all.