What’s in This Book?

This book guides you through the process of creating an Apple Watch app. You’ll learn about the kinds of apps you can make for the device, features available to you, and development paradigms you’ll use as a watch app developer. By the end of this book, you’ll be able to create engaging, full-featured apps for the watch that also interface with their companion iPhone apps, joining forces to create amazing experiences for your users. Here’s a quick rundown of what you’ll learn in each chapter:

Chapter 1: An Overview of Apple Watch

In this chapter you’ll learn the basics of the watch: what it can do, what apps on it are like, and how to decide which features of your iPhone app to bring along to your watch app.

Chapter 2: WatchKit Extension Overview

A WatchKit extension is where your watch app code will live, and this chapter covers what WatchKit extensions are, how they relate to iPhone apps, and how to test them on real devices.

Chapter 3: WatchKit User Interfaces

This chapter dives into the various user-interface (UI) elements available to you on Apple Watch. You’ll learn what they are, how to use them, and the layout system that positions them onscreen. You’ll also start TapALap, the example app we’ll create together.

Chapter 4: Organizing Your UI with Groups

Expanding on your understanding of the UI layout system that began in Chapter 3, this chapter shows you groups, a way to achieve even more complicated and appealing designs in your app.

Chapter 5: Delivering Dynamic Content with Tables

This chapter introduces you to tables—interface objects you can use to display lists of content to your users. You’ll learn how to create them, how to fill them with data, and how to respond to user interaction with them.

Chapter 6: Navigating Between Interfaces

You’ll compose your watch apps with many screens of content; therefore, a successful app needs to transition from one screen to another. This chapter shows you how, why, and when to move your app to new screens.

Chapter 7: WatchKit Extension Lifecycle

At the heart of any watchOS 2 app is the WatchKit extension. In this chapter you’ll learn about the proper care and feeding for a WatchKit extension to unlock powerful functionality and become a best-in-class watch app.

Chapter 8: Communicating with WatchConnectivity

No app these days is complete without networking, so this chapter shows you how to send and receive data from outside your watch app. Whether you’re talking to a server on the Internet or just to your companion iPhone app, you’ll learn how to extend your app’s reach beyond the wrist.

Chapter 9: Creating Complications with ClockKit

Building a watch app that users launch is cool. You know what’s cooler? Building an app that shows up on their watch face every time they so much as look at their watch. The extra features on the watch face are called complications, and this chapter will teach you how to make your own.

Chapter 10: Extending Complications with Time Travel

Complications are a deep topic, so this chapter picks up where the previous one left off to cover time travel—showing information about the past and future—in your complications, as well as animations between them!

Chapter 11: Getting Personal with Sensor Data and HealthKit

The Apple Watch includes a host of onboard sensors, and this chapter will teach you how to take advantage of them. We’ll also use HealthKit to activate the heart rate monitor and use it to track a workout!

Chapter 12: Unlocking Watch App Performance

The most useful watch app in the world with the cleanest, most amazing user interface is useless if it can’t load before the watch screen deactivates. This chapter will show you all kinds of tips and tricks to maximize the performance of your app.

Chapter 13: Being a Good Watch App Citizen

If there’s one thing Apple Watch customers appreciate, it’s attention to detail. This chapter will show you how to make a watch app that respects all users’ physical and mental abilities, speaks to them in their native language, and uses the units of measure they’re comfortable with. By doing that, you’ll have achieved the final bit of spit and polish for an amazing watchOS app experience.