Snapshots and the Dock

watchOS 3 introduces the Dock, which provides a quick way for users to view and launch their favorite apps. After pressing the side button to reveal the Dock, users scroll through it to view snapshots of their favorite apps. When users stop scrolling and let the Dock settle for a moment, the currently displayed app wakes and its snapshot is replaced by the running app.

The system automatically takes periodic snapshots of your app and uses them to populate the Dock and to serve as your app’s launch image. You can update both the currently presented interface controller and the controller’s content before the snapshot is taken. To learn more, see WKSnapshotRefreshBackgroundTask.

Background Tasks

Background tasks give your app time to run in the background and ensure that the information users want is available before they open your app. watchOS 3 introduces several types of background tasks:

• Background App Refresh. Use the WKApplicationRefreshBackgroundTask class to update your app’s state in the background. You often use a background app refresh task to drive other tasks. For example, you might use a background app refresh task to start an NSURLSession background transfer or to schedule a background snapshot refresh task.

• Background Snapshot Refresh. Use the WKSnapshotRefreshBackgroundTask class to update your app’s user interface. You can push, pop, or present other interface controllers, and then update the content of the desired interface controller. The system automatically takes a snapshot of your user interface as soon as this task completes.

• Background Watch Connectivity. When you receive background data from the paired iPhone, the system launches your app in the background, instantiates a WKWatchConnectivityRefreshBackgroundTask object, and passes the task object to your extension delegate’s handleBackgroundTasks: method.

• Background URL Session. When a background transfer requires authorization, or when a background transfer completes (successfully or unsuccessfully), the system creates a background NSURLSession event, instantiates a WKURLSessionRefreshBackgroundTask object, and passes the task object to your extension delegate’s handleBackgroundTasks: method

To learn more about handling background tasks in general, see Background Refresh Tasks.

Complications Enhancements

Complications are small visual elements that appear directly on the watch face. In watchOS 3, creating one or more complications gives your app the opportunity to provide vital pieces of information to users whenever they glance at the watch face.

There are several reasons why you should take advantage of the enhanced complications APIs in watchOS 3:

• Users can launch your app simply by tapping one of your complications.

• The presence of a complication on the watch face tells the system to keep the associated app in a ready-to-launch state. That is, the system attempts to launch your app in the background, keep it in memory, and give it additional time to update.

• A complication is guaranteed to receive 50 push updates per day.

• Adding a complication bundle to your iOS app features your complications in the Apple Watch Face Gallery (to learn more, see Adding Complications to the Gallery).

• The Photo, Timelapse, Motion, and Extra Large watch faces support complications.

In watchOS 3, you can use WKApplicationRefreshBackgroundTask to update complications.

The ClockKit framework (ClockKit.framework) includes several new templates for the extra large complications family, such as CLKComplicationTemplateExtraLargeColumnsText and CLKComplicationTemplateExtraLargeRingImage. In addition, the CLKTextProvider class introduces methods you can use to create localizable text providers, such as localizableTextProviderWithStringsFileTextKey:.

User Notifications

watchOS 3 introduces the User Notifications framework (UserNotifications.framework), which supports the delivery and handling of local and remote notifications. You can use the classes of this framework to schedule the delivery of local notifications based on specific conditions, such as a date or time or after a time interval, and to receive and handle local and remote notifications when they are delivered to the user’s device. To learn more, see User Notifications Framework Reference.

Proactive Suggestions

In watchOS 3, the NSUserActivity object includes the mapItem property, which lets you provide location information that can be used in other contexts. For example, if your app displays hotel reviews, you can use the mapItem property to hold the location of the hotel the user is viewing so that when the user switches to a travel planning app, that hotel’s location is automatically available.

Apple Pay Enhancements

In watchOS 3, the PassKit framework (PassKit.framework) adds support for in-app payments on Apple Watch. In-app payments allow users to securely provide payment and contact information to pay for physical goods and services.

Specifically, PassKit introduces the new PKPaymentAuthorizationController class, which presents an interface in which the user can authorize a payment request, and the PKPaymentAuthorizationControllerDelegate protocol, which you implement to respond to user interaction with the payment authorization controller object. To learn about additional changes in the PassKit framework, see PassKit.

Enhancements for Workout Apps

In watchOS 3, workout apps can run in the background. To enable your workout app to run in the background and access HealthKit data, you must add the WKBackgroundModes key to your Info.plist file and give it the value workout-processing.

You can also launch your watchOS workout app from your iOS app. In your iOS app, call the new startWatchAppWithWorkoutConfiguration:completion: method to launch (or wake up) your workout app on the paired Apple Watch. To learn about additional API changes in the HealthKit framework, see HealthKit.

WatchKit Framework Enhancements

In addition to classes that support background tasks (described in Background Tasks), the WatchKit framework (WatchKit.framework) also includes the following enhancements:

• The new WKCrownSequencer class gives you information about the current state of the digital crown and the new WKCrownDelegate protocol helps you implement a delegate that can receive receive notifications as the user rotates the crown.

• The WKExtension class introduces the applicationState method and WKApplicationState constants, which you can use to track the runtime state of your Watch app. The WKExtension class also includes two methods that help you schedule background tasks: scheduleBackgroundRefreshWithPreferredDate:userInfo:scheduledCompletion: and scheduleSnapshotRefreshWithPreferredDate:userInfo:scheduledCompletion:.

  The WKExtensionDelegate protocol introduces the applicationWillEnterForeground and applicationDidEnterBackground methods, which help you monitor app state changes and the handleBackgroundTasks: method, which tells the delegate when the app has received a background task.

• The new WKGestureRecognizer class is the base class for four concrete subclasses that you can use to access the state of the gesture recognizer and perform custom actions. To learn how to use the concrete subclasses, see WKLongPressGestureRecognizer, WKPanGestureRecognizer, WKSwipeGestureRecognizer, and WKTapGestureRecognizer.

• The new WKInterfaceHMCamera class gives you access to an interface object that includes a representation of data from a HomeKit IP camera.

• The new WKInterfaceInlineMovie class lets you display a poster image for your video that’s replaced by video playback when the user taps the image.

• The new WKInterfacePaymentButton class lets you provide an Apple Pay payment button in your interface. (To initiate a payment request, you must connect the button to a custom action method.)

• The new WKInterfaceSCNScene class gives you an interface object you can use to manage SceneKit content for display in your app.

• The new WKInterfaceSKScene class defines an object you can use to manage a SpriteKit scene in your app.

Watch Connectivity Framework Enhancements

The WCSession class introduces the hasContentPending property, which indicates whether the session has data received in the background that still needs to be delivered to the delegate. WCSession also defines the remainingComplicationUserInfoTransfers property, which indicates the remaining number of times you can send complication data from your iOS app to your WatchKit extension.

Security and Privacy Enhancements

watchOS 3 introduces several changes and additions that help you improve the security of your code and maintain the privacy of user data. To learn more about these items, see https://developer.apple.com/security/.

• App Transport Security (ATS) will be required at the end of 2016 for all network connections outside of a web view. Upcoming policy improvements to ATS include requiring forward secrecy and Transport Layer Security (TLS) v1.2 with SHA-2.

• The SecKey API includes improvements for asymmetric key generation. Use the SecKey API instead of the deprecated Common Data Security Architecture (CDSA) APIs.

• Starting at the end of 2016, the SSLv3 cryptographic protocol and the RC4 symmetric cipher suite will no longer be supported. It’s recommended that you stop using the SHA-1 and 3DES cryptographic algorithms as soon as possible.

• You must statically declare your app’s intended use of protected data classes by including the appropriate purpose string keys in your Info.plist file. For example, you must include the NSCalendarsUsageDescription key to access the user’s Calendar data. If you don’t include the relevant purpose string keys, your app exits when it tries to access the data.

Existing Frameworks Now Available in watchOS

watchOS 3 includes several frameworks that currently exist on other platforms.

The SceneKit framework (SceneKit.framework) lets you integrate 3D models into your app’s UI. SceneKit combines a high-performance rendering engine with a high-level, descriptive API and supports the import, manipulation, and rendering of 3D assets.

Use the WKInterfaceSCNScene class to add live 3D rendered content to your watchOS app or game. In the WatchKit interface, display content by assigning an SCNScene object, which is loaded from a .scn file created in Xcode and bundled in your Watch app’s resources.

SceneKit in watchOS supports most of the features you use on other platforms, including lighting and shading, animation, physics, and particle systems, with the following exceptions:

• 3D spatial audio implemented using SCNAudioSource or SCNAudioPlayer. Instead, use playAudioSource:waitForCompletion: or the WatchKit sound or haptic APIs.

• Custom Metal or OpenGL shader programs implemented using SCNProgram or SCNTechnique. Instead, customize SceneKit rendering with shader modifiers (to learn more, see SCNShadable).

• Core Image filters for node rendering implemented using the SCNNode filters property. Instead, customize rendering with shader modifiers (see SCNShadable).

• The physically-based material and lighting and HDR camera effects introduced in iOS 10, tvOS 10, and OS X v10.12.

The SpriteKit framework (SpriteKit.framework) is a graphics rendering and animation infrastructure that you can use to animate arbitrary textured images, also known as sprites.

Use the WKInterfaceSKScene class to add interactive 2D animation to your watchOS app or game. In the WatchKit interface, display content by assigning an SKScene object, which is loaded from a .sks file created in Xcode and bundled in your Watch app’s resources.

SpriteKit in watchOS supports most of the features you use on other platforms, including actions, physics, lighting, and particle systems, with the following exceptions:

• 3D spatial audio implemented using SKAudioNode. Instead, use playSoundFileNamed:waitForCompletion: or WatchKit sound or haptic APIs.

• Video playback implemented using SKVideoNode. Instead, use WKInterfaceMovie.

• Core Image filters, such as those provided by filter, textureByApplyingCIFilter:, and transitionWithCIFilter:duration:. Use the SKShader class and built-in SKTransition effects to customize node rendering.

The AVFoundation framework (AVFoundation.framework) helps you manage and play audio.

The CloudKit Framework (CloudKit.framework) provides interfaces for moving data between your app and your iCloud containers.

The Core Audio framework (CoreAudio.framework) provides data types that help you represent audio streams, complex buffers, and time values.

The GameKit framework (GameKit.framework) helps you create great social games.

Additional Framework Enhancements

In addition to the major changes described above, watchOS 3 includes many other improvements.