Swift Development for the Apple Watch

Chapter 4. Notifications

When you receive an email, iMessage, or tweet, applications on your iPhone have the ability to show a notification on the screen. These notifications are generally limited in terms of what they can do: they can display a message, play a sound, and also update the badge number on the application’s icon.

With an Apple Watch, notifications that appear on the phone are also displayed on the watch. If you don’t do anything, the watch simply displays the notification message (if one is present) alongside the iOS application’s icon. This means that you don’t need to take your phone out of your pocket when you feel it vibrate; instead, you just need to quickly look at your watch.

However, WatchKit allows you to add more functionality to the notification system, and go beyond simply displaying a message. Your app can provide a custom interface, which takes the contents of the notification that the phone received and presents it using interface elements that are entirely under your control.

In addition to simply presenting messages, notifications can also be actionable. Starting in iOS 8, notifications gained the ability to have actions: notifications could have buttons attached to them, allowing the user to perform some task without having to unlock his phone or leave his current app. These actions can be configured to appear based on different kinds of notifications; for example, when one of your friends checks in somewhere on the location-sharing app Swarm, the ...