grand-central-dispatch

I have an app that needs to send data (using POST) to a server. This function has to be on one of the NavigationController sub-controllers and user should be able to navigate away from this controller and/or close the app (only iPhone4/iOS4 will be supported). Should I use threads/NSOperations or/and send data using existing asynchronous methods? Any ideas/best practices how to implement this? OK, I'll answer my own question. First, like tc said, it's better to have this call on the application delegate, so that the View in the NavigationController can be closed. Second, mark beginning of the

I learned iOS programming thanks to Stanford's CS193p course (on iTunes U) as well as the iOS programming book from Big Nerd Ranch. In both of those, they recommend using dispatch_async() , dispatch_get_main_queue() , etc. to handle threading and concurrent operations. However, at WWDC 2012's session on building concurrent UI, the speaker recommended the use of NSOperationQueue . What are the differences between dispatch_*() and NSOperationQueue , and is there any reason (technical, performance, stylistic, or otherwise) that I should use one over the other? Is NSOperationQueue just an

I have a function doEverything that takes a completion block. It calls two other functions, doAlpha and doBeta which both have completion blocks. These two functions should run asynchronously. I want to call doEverything 's completion block after both of the other functions have called their completion blocks. Currently, it looks like this: func doEverything(completion: @escaping (success) -> ())) { var alphaSuccess = false var betaSuccess = false doAlpha { success in alphaSuccess = success } doBeta { success in betaSuccess = success } // We need to wait here completion(alphaSuccess &&

I have this block of code: DispatchQueue.main.asyncAfter(deadline: .now() + (delay * Double(isDelayAccounted.hashValue)) + extraDelay) { self.isShootingOnHold = false self.shoot() self.shootingEngine = Timer.scheduledTimer(timeInterval: (Double(60)/Double(self.ratePerMinute)), target: self, selector: #selector(ShootingEnemy.shoot), userInfo: nil, repeats: true) } Now, I want to be able to stop this thread from executing. How can I stop it from being executed? For instance, after 3 seconds, I decide I don't want that to execute anymore so I want to stop it. You can use DispatchWorkItem s. They

This code dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ NSLog(@"Main Thread? %d", [NSThread isMainThread]); }); shows that I'm in the main thread. Even doing this: queue = dispatch_queue_create("nonMainQueue", NULL); still reports that I'm in the main queue. This is, it seems, because I'm using dispatch sync . Does this mean that my code is the same as not using dispatch_sync at all? Also: what's the point of dispatch_sync if it does nothing at all, then? Because queues are not threads, in order to check if you are on the main 'queue', you must use different code

I understand that all UI updates must be done from Main thread. But purely for the sake of deeper understanding how GCD and dispatch main work: I have a button that runs a network call and in its completionHandler I eventually do: self.layer.borderColor = UIColor(red: 255/255.0, green: 59/255.0, blue: 48/255.0, alpha: 1.0).cgColor self.layer.borderWidth = 3.0 For the color change to happen it takes 6-7 seconds. Obviously if run the above code from main thread it would change the border color immediately. Question1 even though I don't have ANY other code to run, why doesn't the UI changes