One of the best features of UIViewPropertyAnimator is that you can use it to create animations that can be interrupted, reversed, or interacted with. Many of the animations you see in iOS are interactive animations. For instance, swiping on a page to go back to the previous page is an interactive transition. Swiping between pages on the home screen, opening the control center, or pulling down the notification center are all examples of animations that you manipulate by interacting with them.
While the concept of interactive animations might sound complicated, UIViewPropertyAnimator makes it quite simple to implement them. As an example, you'll see how to implement a drawer on the contact detail page in the Hello-Contacts app. First, you'll prepare the view, so the drawer is partially visible in the app. Once the view is all set up, you will write the code to perform an interactive show-and-hide animation for the drawer.
Open Main.storyboard...