A dictionary of custom information associated with the notification.
- iOS 10.0+
- macOS 10.14+
- UIKit for Mac 13.0+Beta
- watchOS 3.0+
For remote notifications, this property contains the entire notification payload. For local notifications, you configure the property directly before scheduling the notification.
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.