A Boolean value indicating whether the operation executes its task asynchronously.
- iOS 7.0+
- macOS 10.8+
- tvOS 9.0+
- watchOS 2.0+
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
When implementing an asynchronous operation object, you must implement this property and return
YES. For more information about how to implement an asynchronous operation, see Asynchronous Versus Synchronous Operations.