Implementing a custom view-controller transition is one of those things that can take a little while to get used to. Implementing custom transitions involves implementing several objects and it's not always easy to make sense of how this works. This section aims to explain exactly how custom view-controller transitions work so you can add one more powerful tool to your developer toolbox.

A nicely-implemented custom view controller transition will entertain and amaze your users. Making your transitions interactive could even ensure that your users spend some extra time playing around with your app, which is exactly what you want. You will implement a custom transition for the Hello-Contacts app.

First, you'll learn how you can implement a custom modal transition. Once you've implemented that, you will learn about custom transitions for UINavigationController so you can show and hide the contact details page with a custom transition. The dismissal of both the modal view controller and the contact detail page will be interactive, so users can swipe to go back to where they came from.

In this section, you will work through the following steps:

1. Implement a custom modal presentation transition.
2. Make the transition interactive.
3. Implement a custom UINavigationController transition.