Sam Soffes walks us through an elegant way to handle 4-digit PIN input, for cases where you have a software lock screen to your app, or perhaps a 4 digit confirmation code is sent to you via SMS and you need to type it in to continue. Often this type of thing is done with four text fields side-by-side, with awkward delegate implementations to manage focus, etc. Instead, Sam shows us how to leverage the UIKeyInput protocol and create a much cleaner implementation.