via Prototyping UIView Animations in a Swift Playground – Possible Mobile.
Creating UIView animations can be tedious work. Getting the animation in place and functioning is often only the first challenge. Polishing the animation can take just as much time and effort. This polishing phase usually involves making many small tweaks. With each of those small adjustments comes building and running the app followed by navigating to a view where the animation occurs. Playgrounds can make this process more efficient by cutting out some of time spent building and running and all of the time spent navigating.