Apple Watch for Developers

underlining. The app automatically backs up your changes locally until you’re ready to share your creation. When you’re ready, you can press the share button and choose where to share the resulting Infinitweet to. Part of the beauty of Infinitweet is that it all happens locally on the phone. While there is no network access involved in creating the Infinitweet, you of course need network access to share to Twitter, Facebook, or anywhere else online.

Coverage in this chapter will include: Connecting UI buttons/controls to @IBOutlets, navigating between WKInterfaceControllers, working with synced Twitter accounts, using WKInterfaceTables to present options, working with synced iPhone app settings, showing Success/Error messages, and more.

Chapter 4: Processing Audio & Notation

Notation is an iOS app that converts microphone audio into musical score. Whereas sheet music apps available on the App Store now only convert from MIDI signals, Notation converts the audio right from your device’s microphone meaning you can write your musical ideas absolutely anywhere. Notation for Apple Watch furthers this idea by giving the user a real time display of any note they sing or play into the device, allowing users to learn how to read music easier than ever before. The watch itself takes the frequency that the iPhone has detected using an FFT algorithm and translates that into visual information. The watch is constantly looping through the data sent from the iPhone and displaying that information as physical notes on screen. The processing of the audio is actually done on the iPhone in order to minimise memory leak on the watch. The original plan was to process the audio entirely on the watch however it became apparent that this wouldn't allow for that smooth a transition between notes so the author quickly switched the audio processing over to the phone. Notation makes use of Xcode's "App Groups" in order to store and transfer information between the iPhone and the Apple Watch. Coverage will include:

1) User interface on the Apple Watch - Outline problems like when you wish to stack objects on top of each other and Apple's suggestion of not wasting space on branding - talk about solutions.

2) Frequency detection from the iPhone's microphone - As discussed, the author won't go into detail about how Notation does this precisely however he would feel it beneficial to highlight an issue in that Apple hasn’t currently released the full documentation for access to the Apple Watch's microphone so for the time being developers have to rely on the iPhone's microphone. I’d also like to talk about how the bulk of Notation’s processing is done on the iPhone due to the Apple Watch not being able to handle it all itself.

3) Working with App Groups to send and receive data - (Sending button presses from the Apple Watch to the iPhone and receiving frequency data back etc.)

4) Translating data received from the iPhone and using it to display each note on screen.

Chapter 5: Calendar, Stopwatch & Timer Examined

This chapter will examine two applications that the Apple Watch will be successful for. The first is the Calendar app. The author will deconstruct how they are delivering push notifications to the user as well as how to send data back and forth from iCloud. iCloud is such an essential part of app development on iOS these days, so it’s beneficial to outline the best practices in this book. The second app that will be deconstructed is the Stopwatch & Timer. The best Apple Watch apps will perform functions that take very few taps of a button. Therefore, this chapter will explain how these interactions are handled, as well as the code behind timing something as accurately as possible.

Chapter 6: GPS, iBeacon and American Airlines

One of the developers behind American Airlines’ Apple Watch App will show an example of an application that uses both GPS and iBeacon location information to display the most relevant information for a user at a particular point in time. The app detects the user's location and mixes it with information known from a back-end system (flights in the the case of American Airlines) to provide a very simple and clear UI on the Apple Watch.

Chapter 7: Banking Transfers and Communicating with Cordova at FairFX

The app covered in this chapter presents a different situation to the readers. FairFX has their company app in Cordova, which means that they can use the same code base for iOS as well as Android. This presents some issues when you want to do something that needs native code such as the Watch apps because it’s difficult to communicate between the two. For this app, they needed the Apple Watch to be able to read information within their main app to get card balances and exchange rates so they created some code that would store some data within an App Group, which could then be used by the Watch to get the same data the phone app was using.

FairFX (www.fairfx.com) offers money transfers via pre-paid credit cards, bank transfers and actual travel cash. Their mobile app itself is primarily used to top up the pre-paid credit cards but also offers bank transfers. The first release of their Watch Kit app is being used to give their customers the latest exchange rates they are offering. This is read from a JSON feed on their servers and refreshed every 5 minutes but can also be refreshed manually. They also have a push notification to the watch if they specifically want to notify users of a change in rates.

They are also adding an extra update in the near future to give users the balance of their pre-paid cards directly to their watch to save them from taking their phones out of their pockets. On the technical side of this, it presents a challenge as you can’t directly communicate between Cordova and WatchKit, so they have set up some shared storage using App Groups, which both apps can read and write to so that they are using the same data. This would be useful to native Apple devs as well as the range of devs using Cordova/Phonegap, or even other cross platform development tools like Unity or Xamarin.