Discussion
議論
By default, Progress
objects are cancelable.
You typically use this property to communicate whether controls for canceling appear in a progress-reporting user interface. Progress
itself doesn’t do anything with this property other than help pass the value from progress reporters to progress observers.
If an Progress
is cancelable, implement the ability to cancel progress either by setting a block for the cancellationHandler
property, or by polling the isCancelled
property periodically while performing the relevant work.
It’s valid for the value of this property to change during the lifetime of an Progress
object. By default, Progress
is KVO-compliant for this property. It sends notifications on the same thread that updates the property.