Add a process object as a child of a progress tree. The inUnitCount indicates the expected work for the progress unit.
- iOS 9.0+
- macOS 10.11+
- Mac Catalyst 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
NSProgressinstance to add to the progress tree.
The number of units of work to be carried out by the new child.
The child will be assigned a portion of the receivers total unit count based on
in. For more information, see Creating a Tree of Progress Objects.