The current progress shown by the receiver.
- iOS 2.0+
- Mac Catalyst 13.0+
- tvOS 9.0+
The current progress is represented by a floating-point value between 0.0 and 1.0, inclusive, where 1.0 indicates the completion of the task. The default value is 0.0. Values less than 0.0 and greater than 1.0 are pinned to those limits.