The conditions that trigger the delivery of the notification.
- iOS 10.0+
- macOS 10.14+
- tvOS 10.0+
- watchOS 3.0+
For notifications that have already been delivered, use this property to determine what caused the delivery to occur. For remote notifications, this property contains a
UNPush object. For other notifications, the type is based on the trigger condition specified in the original request.