佳为好友

UPDATE: Instruments shows leaks-a-plenty when I do this. Proceed with caution! I'm keeping this here in case I'm actually on to something and someone else can figure out how to get over the leak hurdle.

Here's a twisted idea, which I'm re-trying as I type this:

Set the operation as the object for NSInvocationOperation's initWithTarget:selector:object: method. Presuming you already have a NSOperationQueue (we'll call it queue):

NSInvocationOperation *operation = [NSInvocationOperation alloc];
 operation = [operation initWithTarget:self selector:@selector(myOperation:) object:operation];
 [queue addOperation:operation];
 [operation release];
 

Note that we have to break apart the alloc into its own call. Otherwise we can't set object to operation!

Then, within your operation method, cast the object back and sprinkle checks for isCancelled as desired. For example:

 - (void)myOperation:(id)object {
     NSInvocationOperation *operation = (NSInvocationOperation *)object;
     if ([operation isCancelled]) return;
     ...
   }
 

Make sure your selector ends with a colon back in the initWithTarget:... call, since you'll be passing in an object now.

So far, so good. Now if I can force cancelAllOperations, I'll know if this actually works. :)

+++++