grand-central-dispatch

I get runtime errors which seem to result from my incorrect implementation of GCD in combination with my custom NSManagedObjects. Nested in a GCD call, I am using custom NSManagedObjects which (seem to) have their own managed object contexts (= self.managedObjectContext ). I am creating the managed object context in the app delegate by using the managed object context provided by UIManagedDocument : self.managedDocument.managedObjectContext . I don't understand how to pass the correct managed object context down to my custom NSManagedObjects. How would I need to change my code to use the

When you use threads, do you have any preferences? In general rule, to use any of these techniques : create a new thread manually and use the run loop use NSOperationQueue or use Grand Central Dispatch and the C version with dispatch_queue? Does NSOperationQueue simplify everything, and thus is better to be used when we need to create an asynchronous function? I'm lazy, so my philosophy is to pick the simplest solution that does everything I need it to. (I like to think this is the "lazy" espoused by Larry Wall but sometimes I wonder.) So my order of preference would be: Asynchronous method

I'm seeing an intermittent deadlock in my app when using dispatch_sync on a custom concurrent dispatch_queue. I'm using something similar to the method described in Mike Ash's blog to support concurrent read access but threadsafe mutations on an NSMutableDictionary that acts as a cache of currently active network RPC requests. My project uses ARC. I create the queue with: dispatch_queue_t activeRequestsQueue = dispatch_queue_create("my.queue.name", DISPATCH_QUEUE_CONCURRENT); and the mutable dictionary with NSMutableDictionary *activeRequests = [[NSMutable dictionary alloc] init]; I read

Many apps such as Tweetbot , Twitterrific , Alien Blue , etc. that display images from an API seem to load them in an asynchronous manner. It seems the initial viewable images are loaded synchronously – that is the initial viewable cells aren't displayed until their images are ready – but when scrolling further down past the initial viewable cells, it seems the images for those new cells are loaded independently of the initial synchronous load. For example, when the user loads tweets in a Twitter app, the initial six or seven tweets that will be visible aren't shown until the images for the

I recently switched from using kqueue to GCD dispatch sources to monitor file changes. This has worked out well and resulted in a much simpler API. I documented my switch here . The only issue I have is that now I cannot access the flags on the event that I was able to in kqueue. For example with kqueue I was able to check if the file was deleted, renamed, or it's attributes were changed with the following: struct kevent event; ... if(event.flag & EV_DELETE) { printf("File was deleted\n"); } Is this API not available with GCD or do I need to set up dispatch sources up for each flag I would