grand-central-dispatch

I created a game in Swift that involves monsters appearing. Monsters appear, and disappear, based on timers using something like this: func RunAfterDelay(_ delay: TimeInterval, block: @escaping ()->()) { let time = DispatchTime.now() + Double(Int64(delay * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC) DispatchQueue.main.asyncAfter(deadline: time, execute: block) } and then I'd just call it like this (for example to spawn after 2 seconds): ///Spawn Monster RunAfterDelay(2) { [unowned self] in self.spawnMonster() } I then do something similar for hiding (after x seconds, I despawn the monster).

How can I check for equality between dispatch_queue_t vars? dispatch_queue_t currentQueue = dispatch_get_current_queue(); dispatch_queue_t mainQueue = dispatch_get_main_queue(); if (currentQueue == mainQueue) { } from the docs: typedef struct dispatch_queue_s *dispatch_queue_t; I'm not sure but does this mean that it's a pointer to a dispatch_queue_s struct? Since I can't check equality on pointers, I'm not sure how can I check if a dispatch_queue_t is the same as another? This depends on the queue you're on. In this particular case use: if ([NSThread isMainThread]) {} In general, you can use

So far I have gone through the doc of GCD, however it seems there misses dispatch_cancel() which I want to use it to cancel all dispatch's blocks invocation. Is there any way to implement dispatch_cancel()? As @HampusNilsson mentions, you can't reasonably cancel any in-flight operation in a non-garbage collected environment (such as this) because it would inherently leak resources and leave the process in an indeterminate state. NSOperationQueue has a cancellation API, and that API can be used to implement cancellation of in-flight operations, provided that the operations themselves are

I'm acquiring data from a database asynchronously. Is there any way I can limit the concurrent requests to a number, but still execute the rest? I saw a post using NSOperation and NSOperationQueue but this is too complicated for me. Is there any other ways to do it? Can GCD achieve it? Something like this: ... //only make one of these obviously :) remaking it each time you dispatch_async wouldn't limit anything dispatch_semaphore_t concurrencyLimitingSemaphore = dispatch_semaphore_create(limit); ... //do this part once per task, for example in a loop dispatch_semaphore_wait

I am developing an app where i want to call method in separate queue using dispatch_async . I want to call that method repeatedly after certain interval of time. But the method is not getting called. I don't know whats wrong. Here is my code: dispatch_async( NotificationQueue, ^{ NSLog(@"inside queue"); timer = [NSTimer scheduledTimerWithTimeInterval: 20.0 target: self selector: @selector(gettingNotification) userInfo: nil repeats: YES]; dispatch_async( dispatch_get_main_queue(), ^{ // Add code here to update the UI/send notifications based on the // results of the background processing }); })

I'm using the code example by David Hamrick to monitor a file using GCD. int fildes = open("/path/to/config.plist", O_RDONLY); dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_VNODE,fildes, DISPATCH_VNODE_DELETE | DISPATCH_VNODE_WRITE | DISPATCH_VNODE_EXTEND | DISPATCH_VNODE_ATTRIB | DISPATCH_VNODE_LINK | DISPATCH_VNODE_RENAME | DISPATCH_VNODE_REVOKE, queue); dispatch_source_set_event_handler(source, ^ { //Reload the config file }); dispatch_source_set_cancel_handler(source, ^ { /