Before we can begin using notifications within our Shopping List application, we need to get a better understanding of how they work within the WatchKit framework. We did touch on this in Chapter 2, Understanding Apple Watch, so much of this will be quite familiar.
In the next section, we will talk a bit about the notification controller life cycle; you will notice that the notification controller inherits all of the existing functionality of the WKInterfaceController class and contains a variety of method calls that help determine whenever a notification becomes active or the controller context instance becomes awake.
As we mentioned in the introduction to the chapter, notifications that appear on an iOS device will also appear on Apple Watch, which means that you don't need to physically take your phone out of your pocket whenever you feel it vibrating. You can simply just glance at your watch and respond to the action accordingly.
The WatchKit framework...