grand-central-dispatch

I have my own method that takes a block as an argument. I want to keep track of that block inside an NSDictionary. What is the best way to add the block to the dictionary? I tried this code but after executing the line below (setObject...) the dictionary is still empty. I presume that is because the block is not of type NSObject. But what is the right way to do this? - (void)startSomething:(NSURLRequest*)request block:(void (^)(NSURLResponse*, NSData*, NSError*))handler { NSURLConnection *connection = [NSURLConnection connectionWithRequest:request delegate:self]; [pendingRequests setObject

What is the order of operations on iOS? I'm thinking sepcifically about timing of setNeedsLayout and layoutSubviews setNeedsDisplay and drawRect touch recognition [NSTimer scheduledTimerWithTimeInterval:0.000001 tar(...)] dispatch_async(dispatch_get_main_queue(), ^{ /* code */} As an example of an answer I would like to receive it could be in this format: dispatch_async on main Happens before the next runcycle drawRect Happens at the end of the runcycle rob mayoff (Parts of this are copied from my answer to a similar question .) It turns out that the run loop is complicated, and a simple

What are the differences between Operation Queue and Dispatch Queue? Under what circumstances will it be more appropriate to use each? NSOperationQueue predates Grand Central Dispatch and on iOS it doesn't use GCD to execute operations (this is different on Mac OS X). It uses regular background threads which have a little more overhead than GCD dispatch queues. On the other hand, NSOperationQueue gives you a lot more control over how your operations are executed. You can define dependencies between individual operations for example, which isn't possible with plain GCD queues. It is also

I am trying to get my head around the concepts of Grand Central Dispatch. I want to understand these quotes from Vandad's book on Concurrent Programming. The real use for GCD is to dispatch tasks to multiple cores , without making you the programmer, worry about which core is executing which task. and At the heart of GCD are dispatch queues. Dispatch queues are pools of threads . and finally You will not be working with these threads directly. You will just work with dispatch queues, dispatching tasks to these queues and asking queues to invoke your task. I have bolded the key terms. Are

I want to download some files, for example 100 files, at the same time. So I decided to add my download threads to a dispatch queue, and GCD will adjust how many threads will run at the same time. The problem here is: the block in dispatch_async will be completed immediately, because task will run on another thread. So, if urls 's length is 100, it will create 100 threads immediately. var queueDownloadTask = dispatch_queue_create("downloadQueue", nil) for url in urls { dispatch_async(queueDownloadTask) { let config = NSURLSessionConfiguration.defaultSessionConfiguration() let

I created some test code for NSThread and Grand Central Dispatch (GCD): - (void)doIt:(NSNumber *)i { sleep(1); NSLog(@"Thread#%i", [i intValue]); } - (IBAction)doWork:(id)sender { for (int i = 0; 10 > i; i++) { NSNumber *t = [NSNumber numberWithInt:i]; [NSThread detachNewThreadSelector:@selector(doIt:) toTarget:self withObject:t]; } sleep(1); dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_apply(10, queue, ^(size_t i) { sleep(1); NSLog(@"GCD#%u",(int)i); }); } And the results: 2011-04-13 19:41:07.806 GDC[1494:5e03] Thread#0 2011-04-13 19:41:07