A value used to identify the user activity.
- iOS 12.0+
- macOS 10.15.4+
- Mac Catalyst 13.0+
- watchOS 5.0+
Set this property to a value that identifies the user activity so you can later delete it with
delete. For example, if the user checks the weather for Cupertino each morning from home, the weather app sets the persistent identifier to the city name (Cupertino). When the user deletes Cupertino from the weather app, the app deletes the user activity associated with the identifier, "Cupertino".