This document provides an overview of creating a WatchKit app for the Apple Watch, which requires pairing with an iPhone. It outlines the app structure, which consists of a WatchKit app for UI resources and a WatchKit extension for code management, and introduces various classes like WKInterfaceController and WKUserNotificationInterfaceController. Additionally, the document details the steps to set up a WatchKit project in Xcode and run the app on a simulator.

1. WatchKit
Create Your First WatchKit App

2. Introduction
 The apple watch requires an iPhone paired with it to run the
apps without an iPhone the watch apps will not work.
 For creating watch app, we need two separate bundles:
 WatchKit app: The WatchKit app contains only storyboard and
resource files associated with our apps UI.
 WatchKit extension: The WatchKit extension contains the code
for managing the WatchKit apps UI and responding user
interactions.

3. App Structure

4. Watch app Launching

5. WatchKit Framework
 The whole apple watch is managed by the few classes the most
used are as :
 WKInterfaceController
 WKUserInterfaceNotificationController
 WKInterfaceDevice
 WKInterfaceObject

6. WKInterfaceController
 WKInterfaceController in WatchKit is as same as
UIViewController in UIKit.
 WKInterfaceController is a lot more restricted and has a
different life cycle. There are different methods to work with as
following.

7. WKUserInterfaceNotificationController
 The WKUserNotificationInterfaceController class manages a
dynamic user interface for a local or remote notification.
 After initializing your interface controller, WatchKit calls the
didReceiveRemoteNotification:withCompletion: or
didReceiveLocalNotification:withCompletion: method to
provide you with the payload data from the notification.

8. WKInterfaceDevice
 This class contains basic information related to the
iWatch.
 This includes:
 Screen bounds
 Scale
 Current locale
 You can also use it to manage your images cache.
WatchKit allows you to store up to 20 MB of cached
images on the iWatch.

9. WKInterfaceObject
 This is the base class for all UI controls supported by WatchKit. As
we cannot use UI views from UIKit. All we can do is use the ones
that WatchKit provides.
 WKInterfaceButton
 WKInterfaceDate
 WKInterfaceGroup
 WKInterfaceImage
 WKInterfaceLabel
 And more..

10. Creating Watch App
 First create a new single view application iPhone project
and call it “WatchKitDemo.”

11. Create WatchKit Target
 Select New > Target... from Xcode's File menu and
choose WatchKit App from the iOS > Apple Watch section on
the left.

12.  Give the project name as “Watch” and uncheck include
notification scene and include Glance scene.

13.  When you click Finish, Xcode will create a number of files,
groups, and targets.
 Xcode will also create a scheme to run the WatchKit application
in the iOS Simulator and it will ask you whether it should
activate that scheme. Click Activate to activate it.

14. Project Anatomy
 By adding a WatchKit application to our project, Xcode has
created two targets for us,
 one for the WatchKit extension, Watch Extension,
 and one for the WatchKit application, Watch App.
WatchKit application
WatchKit Extension

15. Create the user interface
 Open the WatchKitDemo WatchKitApp folder and click on the
Interface.storyboard file.
 You should see a blank watch storyboard interface that you can drag UI
controls onto.

16. Run WatchKit App
 To run Watch application, Select Watch scheme from the
Scheme List and select iPhone+Apple Watch Simulator.

17. Output