nsoperationqueue

Apple's Grand Central Dispatch (GCD) is great, but only works on iOS 4.0 or greater. Apple's documentation says, "[A] serialized operation queue does not offer quite the same behavior as a serial dispatch queue in Grand Central Dispatch does" (because the queue is not FIFO, but order is determined by dependencies and priorities). What is the right way to achieve the same effect as GCD's serial dispatch queues while supporting OS versions before GCD was released? Or put another way, what is the recommended way to handle simple background processing (doing web service requests, etc.) in iOS apps

for example, i have 100 times the for loop. and need to update UIImageView,and the last 2 method is same slowly. why? what is the different between they? //fastest [[NSOperationQueue mainQueue] addOperationWithBlock:^{ [btnThumb setImage:[UIImage imageWithData:data] forState:UIControlStateNormal]; [scrollView addSubview:btnThumb]; }]; //slowly dispatch_async(dispatch_get_main_queue(), ^ { [btnThumb setImage:[UIImage imageWithData:data] forState:UIControlStateNormal]; [scrollView addSubview:btnThumb]; }); //slowly [btnThumb setImage:[UIImage imageWithData:data] forState:UIControlStateNormal];

I am trying to implement asynchronous url requests in a particular function, I want all these requests to complete and then do a particular action but the action precedes the requests i.e, it is getting called before the requests complete. dispatch_queue_t fetchQ = dispatch_queue_create("Featured Doc Downloader", NULL); dispatch_async(fetchQ, ^{ [self myAsyncMultipleURLRequestFunction]; dispatch_sync(dispatch_get_main_queue(), ^{ [self updateUIFunction]; }); }); -(void)myAsyncMultipleURLRequestFunction { for (int i=0; i<count; i++) { NSURLConnection *loginConnection = [[NSURLConnection alloc]

I'm using NSOperationQueue , and NSOperation for running some function on background click. But I want to be able, when user clicks some button, stop that Operation. How can I do it? Something like, [currentoperation stop]; Cancel - won't work me. I want to stop immediately. Thanks You should be calling the -cancel method, and the operation itself has to support being cancelled by monitoring the isCancelled property/keypath and safely stopping when its value becomes YES . If the NSOperation is your own, you will probably have to create a custom subclass to implement this functionality. You

I want to perform few operations and need to start the next operation only upon completion of the previous one. The operation I'm adding will send async call to the server and receive data. I want to start the next operation only after the first call to the server finish receiving data from the server. How to do that? {.... PhotoDownloader *pd = [[PhotoDownloader alloc] init]; [GetGlobalOperationQueue addOperation:pd]; } Inside the PhotoDownloader I will allocate the required parameters and call a Global function which handles all the request [GlobalCommunicationUtil sendServerReq:reqObj