# NSUserActivity

An NSUserActivity object can be used to coordinate significant events in an app with the system. It is the basis for Handoff (opens new window) between different devices running iOS and macOS. Additionally, it may also be used to improve public-indexing and augment or create Spotlight Search results for an app. As of iOS 10, it may also be used to coordinate interactions between your app and Siri using SiriKit.

# Creating a NSUserActivity

To create a NSUserActivity object, your app must declare the types of activities it supports in its Info.plist file. Supported activities are defined by your application and should be unique. An activity is defined using a reverse-domain style naming scheme (i.e. "com.companyName.productName.activityName"). Here is what an entry in your Info.plist might look like:

Key	Value
NSUserActivityTypes	[Array]
- item0	com.companyName.productName.activityName01
- item1	com.companyName.productName.activityName02

Once you have defined all supported activity types, you may begin to access and use them in your application's code.

To create a NSUserActivity object you must do the following

// Initialize the activity object and set its type from one of the ones specified in your app's plist
NSUserActivity *currentActivity = [[NSUserActivity alloc] initWithActivityType:@"com.companyName.productName.activityName01"];

// Set the title of the activity.
// This title may be displayed to the user, so make sure it is localized and human-readable
currentActivity.title = @"Current Activity";

// Configure additional properties like userInfo which will be included in the activity
currentActivity.userInfo = @{@"informationKey" : @"value"};

// Configure the activity so the system knows what may be done with it
// It is important that you only set YES to tasks that your application supports
// In this example, we will only enable the activity for use with Handoff
[currentActivity setEligibleForHandoff:YES];
[currentActivity setEligibleForSearch:NO]; // Defaults to NO
[currentActivity setEligibleForPublicIndexing:NO]; // Defaults to NO

// Set this activity as the current user activity
// Only one activity may be current at a time on a device. Calling this method invalidates any other current activities.
[currentActivity becomeCurrent];

After this, the activity above should be available for Handoff (although more work is required to properly handle the "Handoff").

# Remarks

# Activity Types

Supported activity types must be defined in your app's Info.plist file under the NSUserActivityTypes key. Activities are tied to your Developer Team ID, meaning that activity coordination is restricted between apps that have the same Team ID (e.g. "Safari" could not accept a Handoff activity from "Chrome" or vice versa).

# Becoming / Resigning the Current Activity

Marking an activity as current using becomeCurrent makes it available for Handoff or Spotlight Indexing. Only one activity may be current at a time. You may mark an activity as inactive without invalidating by calling resignCurrent.

If you invalidate an activity, the same instance may not be made current again.

Do not mark an activity as current when providing it for SiriKit (opens new window).

# Search Indexing

Activities are not to be used as a general-purpose indexing mechanism within your app. Instead, they should only be used in response to user-initiated actions. To index all content in your app, use CoreSpotlight.

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