How to stop the current NSOperation?

Question

I use NSOperationQueue and NSOperation to run some function on a background click. But I want the user to stop the operation by pressing a button.

How can i do this?

Something like [currentoperation stop];
Cancel - will not work. I want to stop immediately.

thanks

Answer 1

You must call the -cancel method, and the operation itself must support cancellation by monitoring the / tpath> t21> property and stopping safely when its value becomes YES . If NSOperation is your own, you may have to create your own subclass to implement this function. You cannot (safely) force an arbitrary operation to stop immediately. It must support cancellation.

Answer 2

You cannot stop right away using everything that Apple provides with NSOperation . You can use -[cancel] , as other people suggested, but the current operation will be performed until completion. One way to get closer to using -[isCancelled] inside your operation and sprinkle it throughout the code (especially in long loops). Sort of:

 - (void)main { // do a little work if ([self isCancelled]) { return; } // do a little more work if ([self isCancelled]) { return; } } 

So you will stop soon.

If you really want to stop the flow, you may need to study signal processing. A threaded example is shown here. By sending a custom signal to a specific stream, you can somehow end this stream. It will be a lot more work, and probably a lot more problems than it costs.

Answer 3

you use cancel and check if self ( NSOperation ) was canceled at runtime.