A dictionary of custom information associated with the notification.
- iOS 10.0+
- macOS 10.14+
- tvOS 10.0+
- watchOS 3.0+
Use this property to associate custom information with the notification. The contents of the dictionary are not seen by the user, but are accessible to your app or to any notification-related app extensions.
The keys in this dictionary must be property-list types—that is, they must be types that can be serialized into the property-list format. For information about property-list types, see Property List Programming Guide.