The identifier of the category object that represents the notification's type.
- iOS 10.0+
- macOS 10.14+
- watchOS 3.0+
Use notification types to distinguish between the different types of notifications your app supports. You use this support primarily to create actionable notifications—that is, notifications with custom action buttons—and to redirect your notifications through either your notification service app extension or your notification content app extension.
Assign a value to this property that matches the
identifier property of one of the
UNNotification objects you previously registered with your app. If you assign a string that does not match one of your registered categories, the system displays your notification without custom actions and without routing it through your app extensions.