41. An Introduction to SiriKit

Although Siri has been part of iOS for a number of years, it was not until the introduction of iOS 10 that some of the power of Siri was made available to app developers through SiriKit. Initially limited to particular categories of app, SiriKit has since extended to allow Siri functionality to be built into apps of any type.

The purpose of SiriKit is to allow key areas of application functionality to be accessed via voice commands through the Siri interface. An app designed to send messages, for example, may be integrated into Siri to allow messages to be composed and sent using voice commands. Similarly, a time management app might use SiriKit to allow entries to be made in the Reminders app.

This chapter will provide an overview of SiriKit and outline the ways in which apps are configured to integrate SiriKit support.

41.1 Siri and SiriKit

Most iOS users will no doubt be familiar with Siri, Apple’s virtual digital assistant. Pressing and holding the home button, or saying “Hey Siri” launches Siri and allows a range of tasks to be performed by speaking in a conversational manner. Selecting the playback of a favorite song, asking for turn-by-turn directions to a location or requesting information about the weather are all examples of tasks that Siri can perform in response to voice commands.

When an app integrates with SiriKit, Siri handles all of the tasks associated with communicating with the user and interpreting the meaning and context of the user’s words. Siri then packages up the user’s request into an intent and passes it to the iOS app. It is then the responsibility of the iOS app to verify that enough information has been provided in the intent to perform the task and to instruct Siri to request any missing information. Once the intent contains all of...

41.2 SiriKit Domains

When initially introduced, SiriKit could only be used with apps to perform tasks that fit into narrowly defined categories, also referred to as domains. With the release of iOS 10, Siri could only be used by apps when performing tasks that fit into one or more of the following domains:

•Messaging

•Notes and Lists

•Payments

•Visual Codes

•Photos

•Workouts

•Ride Booking

•CarPlay

•Car Commands

•VoIP Calling

•Restaurant Reservations

•Media

If your app fits into one of these domains then this is still the recommended approach to performing Siri integration. If, on the other hand, your app does not have a matching domain, SiriKit can now be integrated using custom Siri Shortcuts.

41.3 Siri Shortcuts

Siri Shortcuts allow frequently performed activities within an app to be stored as a shortcut and triggered via Siri using a pre-defined phrase. If a user regularly checked a specific stock price within a financial app, for example, that task could be saved as a shortcut and performed at any time via Siri voice command without the need to manually launch the app. Although lacking the power and flexibility of SiriKit domain-based integration, Siri Shortcuts provide a way for key features to be made accessible via Siri for apps that would otherwise be unable to provide any Siri integration.

An app can provide an “Add to Siri” button that allows a particular task to be configured as a shortcut. Alternatively, an app can make shortcut suggestions by donating actions to Siri. The user can review any shortcut suggestions within the Shortcuts app and choose those to be added as shortcuts.

Based on user behavior patterns, Siri will also suggest shortcuts...

41.4 SiriKit Intents

Each domain allows a predefined set of tasks, or intents, to be requested by the user for fulfillment by an app. An intent represents a specific task of which Siri is aware and for which SiriKit expects an integrated iOS app to be able to perform. The Messaging domain, for example, includes intents for sending and searching for messages, while the Workout domain contains intents for choosing, starting and finishing workouts. When the user makes a request of an app via Siri, the request is placed into an intent object of the corresponding type and passed to the app for handling.

In the case of Siri Shortcuts, a SiriKit integration is implemented by using a custom intent combined with an intents definition file describing how the app will interact with Siri.

41.5 How SiriKit Integration Works

Siri integration is performed via the iOS extension mechanism. Extensions are added as targets to the app project within Xcode in the same way as other extension types. SiriKit provides two types of extension, the key one being the Intents Extension. This extension contains an intent handler which is subclassed from the INExtension class of the Intents framework and contains the methods called by Siri during the process of communicating with the user. It is the responsibility of the intent handler to verify that Siri has collected all of the required information from the user, and then to execute the task defined in the intent.

The second extension type is the UI Extension. This extension is optional and comprises a storyboard file and a subclass of the IntentViewController class. When provided, Siri will use this UI when presenting information to the user. This can be useful for including additional information within the Siri user interface...

41.6 Resolving Intent Parameters

Each intent domain type has associated with it a group of parameters that are used to provide details about the task to be performed by the app. While many parameters are mandatory, some are optional. The intent to send a message must, for example, contain a valid recipient parameter in order for a message to be sent. A number of parameters for a Photo search intent, on the other hand, are optional. A user might, for example, want to search for photos containing particular people, regardless of the date that the photos were taken.

When working with Siri domains, Siri knows all of the possible parameters for each intent type, and for each parameter Siri will ask the app extension’s intent handler to resolve the parameter via a corresponding method call. If Siri already has a parameter, it will ask the intent handler to verify that the parameter is valid. If Siri does not yet have a value for a parameter it will ask the intent handler if the...

41.7 The Confirm Method

The confirm method is implemented within the extension intent handler and is called by Siri when all of the intent parameters have been resolved. This method provides the intent handler with an opportunity to make sure that it is ready to handle the intent. If the confirm method reports a ready status, Siri calls the handle method.

41.8 The Handle Method

The handle method is where the activity associated with the intent is performed. Once the task is completed, a response is passed to Siri. The form of the response will depend on the type of activity performed. For example, a photo search activity will return a count of the number of matching photos, while a send message activity will indicate whether the message was sent successfully.

The handle method may also return a continueInApp response. This tells Siri that the remainder of the task is to be performed within the main app. On receiving this response, Siri will launch the app, passing in an NSUserActivity object. NSUserActivity is a class that enables the status of an app to be saved and restored. In iOS 10 and later, the NSUserActivity class has an additional property that allows an NSInteraction object to be stored along with the app state. Siri uses this interaction property to store the NSInteraction object for the session and passes it to the main...

41.9 Custom Vocabulary

Clearly Siri has a broad knowledge of vocabulary in a wide range of languages. It is quite possible, however, that your app or app users might use certain words or terms which have no meaning or context for Siri. These terms can be added to your app so that they are recognized by Siri. These custom vocabulary terms are categorized as either user-specific or global.

User specific terms are terms that only apply to an individual user. This might be a photo album with an unusual name or the nicknames the user has entered for contacts in a messaging app. User specific terms are registered with Siri from within the main iOS app (not the extension) at application runtime using the setVocabularyStrings(oftype:) method of the NSVocabulary class and must be provided in the form of an ordered list with the most commonly used terms listed first. User-specific custom vocabulary terms may only be specified for contact and contact group names, photo tag and album names...

41.10 The Siri User Interface

Each SiriKit domain has a standard user interface layout that is used by default to convey information to the user during the Siri integration. The Ride Booking extension, for example, will display information such as the destination and price. These default user interfaces can be customized by adding an intent UI app extension to the project. This topic is covered in the chapter entitled “Customizing the SiriKit Intent User Interface”. In the case of a Siri Shortcut, the same technique can be used to customize the user interface that appears within Siri when the shortcut is used.

41.11 Summary

SiriKit brings some of the power of Siri to third-party apps, allowing the functionality of an app to be accessed by the user using the Siri virtual assistant interface. Siri integration was originally only available when performing tasks that fall into narrowly defined domains such as messaging, photo searching and workouts. This has now been broadened to provide support for apps of just about any type. Siri integration uses the standard iOS extensions mechanism. The Intents Extension is responsible for interacting with Siri, while the optional UI Extension provides a way to control the appearance of any results presented to the user within the Siri environment.

All of the interaction with the user is handled by Siri, with the results structured and packaged into an intent. This intent is then passed to the intent handler of the Intents Extension via a series of method calls designed to verify that all the required information has been gathered. The intent is then...