Question

I’m working on an iOS project that has to work from iOS4. I have an NSOperationQueue and I add an operation. The main method of the operation looks something like this:

-(void)main 
{
    [self.client getStuffSuccess:^(Stuff *s) {
        //Do something on success
    } failure:^(NSError *error) {
        //Do something on failure
    }
}

The code inside the block will only be called when getStuff calls success or failure. I thought that in the meanwhile, my operation would be removed from the NSOperationQueue and the block wouldn’t be called. However, I tested it and the block was in fact called. It’s called no matter if the client calls the success block on the dispatch_get_main_queue or on the thread that called it – in this case the operation above.

Before the block is called, the method isFinished is actually returning true (I overrode the isFinished method and checked the value), so can someone explain me how is it possible that the block is being called?

I’m asking all this because although this works fine for one call, when I add it in a cycle of a few hundred iterations, I get an EXC_BAD_ACCESS and understanding the above might help me on the debugging.

Answer 1

Since getStuffSuccess:failure is asynchronous, you need to use a concurrent operation. Here is a helpful blog post:
http://www.dribin.org/dave/blog/archives/2009/05/05/concurrent_operations/