In this chapter, you learned how to build a Mac app from an existing iOS app.

We started by refining your app's user interface when running on the iPhone. Next, you added some code to make your app detect the device that it's running on, and modified your app's screens to suit the larger screen of an iPad. You also modified your code so that your app's user interface will automatically change based on the device it's running on. Finally, you used Mac Catalyst to build a Mac app from your iPad app. Your app now works great on iPhone, iPad, and Mac.

You're now able to make your existing iPhone apps run well on iPad, and also to make Mac apps from your iPad apps. As you have seen, once you have an iPhone app, you can make it work on iPad and Mac with relatively little effort.

In the next chapter, you'll learn a completely new way to build user interfaces using SwiftUI, a modern way to declare user interfaces for any Apple platform.