small medium large xlarge

Developing for Apple Watch: Your App on Their Wrists

May 27, 2015

On this day in 1933, Chicago's "Century of Progress" World's Fair opened, featuring innovations in technology, including futuristic looks at pre-fabricated housing, complete with personal helicopter pads.

Well we don't have personal helicopter pads yet, nor do we have personal jetpacks, but we do have the Apple Watch.

The Apple Watch offers the closest connection yet between your iOS app and users. But you can’t just port your existing iPhone app to the watch—you need to learn how to write WatchKit Extensions. Developing for Apple Watch will show you how, now available at

Read on for some Tips and Tricks from Developing for Apple Watch
by Jeff Kelley.

Developing for Apple Watch: Your App on Their Wrists

With the Apple Watch, your app is right there on your user's wrist. This book teaches you how to extend your existing iPhone app with a WatchKit Extension, giving your users quick access to your app’s most important features and an intimate user experience that’s always within arm’s reach.

You’ll learn how to display beautiful interfaces to the user, how to use the iPhone app for heavy number-crunching, and the best way to keep everything in sync across your users’ devices. You'll develop a watch app to take advantage of the best WatchKit has to offer, and by the end of this book, you’ll be ready to ship your own apps to the App Store.

Plus, this book will help focus your efforts. What features make sense on the watch? How should you organize them? How do you tell your users what they can do? You'll learn how to brainstorm to come up with the best strategy for your app.

When your users are proudly showing off their Apple Watch, this book will help you make sure it’s your app on there.

Now available from

Tips and Tricks from Developing for Apple Watch

by Jeff Kelley

Do as little work as possible in your WatchKit Extension.
You want your WatchKit app to be fast, and one of the best ways to do that is to divide your app’s work. Let your WatchKit Extension—the part of your iPhone app that controls the UI on the watch—handle the watch UI, and offload any long-running network requests, processor-intensive computations, or database management-style tasks to your iPhone app. You’ll be able to run your iPhone app code in the background, freeing up your WatchKit Extension for handling user input and updating your interface.

A touch of color goes a long way.
The OLED screen of the Apple Watch gives you better battery life with a black background, but that doesn’t mean that your app has to be all gloom and doom. Black or dark gray backgrounds with a touch of color on the side or in text draw your users’ attention to key elements of the interface without breaking the battery bank.

Make friends with storyboards.
Every piece of user interface in your watch app must first be created in your storyboard; there’s no programmatically creating user interfaces in code. Even if you’ve grown to dislike using storyboards or xibs in iOS development, you’ll be dependent on them for WatchKit user interfaces.

Put your most timely information in your Glance.
Your WatchKit app can have only one Glance—an interface to display to your users quickly from their watch face—so make it count. It’s a place for your users to find your app’s most timely and relevant content, so be sure to give them exactly what they need.

Take advantage of system-provided internationalization.
Apple provides built-in classes to format numbers, dates, units of length, energy, and mass, and more. By using them, your app will automatically use a format that’s appropriate for your users and where they live, letting you spend more time making great apps and less time formatting data.

Test on real watch hardware.
The iOS Simulator, fantastic as it is, is not an entirely faithful reproduction of many hardware characteristics. Before sending your app to the App Store, if at all possible, run your app on a real Apple Watch. You’ll get a better sense of performance, look and feel, and integration with the rest of the watch’s features—including some things that you can’t reproduce on the simulator.

Now available from

Upcoming Author Appearances

  • 2015-05-29 Jeffrey R. Kelley,
    Self.conference, Detroit, MI
  • 2015-06-06 Maik Schmidt,
    Maker Faire Hannover (Germany)
  • 2015-06-15 Andrew Hunt,
    NDC Oslo
  • 2015-06-18 Seb Rose,
    NDC, Oslo
  • 2015-06-25 Adam Tornhill,
    EuroClojure 2015, Barcelona, Spain
  • 2015-06-25 Ian Dees,
    Open Source Bridge, Portland
  • Did You Know?

    Please note our ebooks do not contain any Digital Restrictions Management, and have always been DRM-free. For us, "DRM Free" means "freedom": you should own the books you've paid for. On whatever device is handy—your laptop, iThingy, Blueberry, you name it. We think ideas should outlast any device you put them on.

    And you can always come back and re-download your books when needed, using your account on We're here to make your life easier.

    Don't Get Left Out

    Are your friends jealous that you get these spiffy email newsletters and they don't? Clue them in that all they need to do is create an account on (email address and password is all it takes) and select the checkbox to receive newsletters.

    Are you following us on Twitter and/or Facebook? Here's where you can find us and keep up with the latest news and commentary, and occasional discounts:

    Tell your friends! Tweet this

    Follow us on Twitter: pragprog</a>, <a href="">pragpub, Andy PragmaticAndy</a> and Dave <a href="">pragdave.

    Coming Soon:

    • Deliver Audacious Web Apps with Ember 2
    • Mazes for Programmers: Code Your Own Twisty Little Passages in print
    • Real-World Kanban in print

    Recently Released:

    Thanks for your continued support,

    Andy & Dave
    The Pragmatic Programmers

    Books • eBooks • PragPub Magazine • Audiobooks and Screencasts