A Boolean value indicating whether the operation executes its task asynchronously.
- iOS 2.0+
- macOS 10.5+
- tvOS 9.0+
- watchOS 2.0+
asynchronous property instead.
The value of this property is
YES for operations that run asynchronously with respect to the current thread or
NO for operations that run synchronously on the current thread. The default value of this property is
In macOS 10.6 and later, operation queues ignore the value in this property and always start operations on a separate thread.