NSOperation dealloc not called when cancel operation

Question

I am using NSOperation in my application. I am cancelling the previously executing operation when create another operation. But the previously created operation's dealloc method not calling when cancelling that operation.

Pls suggest me. Thanks.

Answer 1

I think what you need is that isFinished returns YES and isExecuting returns NO after cancelled. Otherwise the operation object will never be released.

Document says.

In addition to simply exiting when an operation is cancelled, it is also important that you move a cancelled operation to the appropriate final state. Specifically, if you manage the values for the isFinished and isExecuting properties yourself (perhaps because you are implementing a concurrent operation), you must update those variables accordingly. Specifically, you must change the value returned by isFinished to YES and the value returned by isExecuting to NO. You must make these changes even if the operation was cancelled before it started executing.

Answer 2

That's just fine:

Responding to the Cancel Command

Once you add an operation to a queue, the operation is out of your hands. The queue takes over and handles the scheduling of that task. However, if you decide later that you do not want to execute the operation after all—because the user pressed a cancel button in a progress panel or quit the application, for example—you can cancel the operation to prevent it from consuming CPU time needlessly. You do this by calling the cancel method of the operation object itself or by calling the cancelAllOperations method of the NSOperationQueue class.

Canceling an operation does not immediately force it to stop what it is doing. Although respecting the value returned by the isCancelled is expected of all operations , your code must explicitly check the value returned by this method and abort as needed. The default implementation of NSOperation does include checks for cancellation. For example, if you cancel an operation before its start method is called, the start method exits without starting the task.

The dealloc method will be called when the retain count of the object gets to zero alas when no other object is using it.