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dispatch_queue_t aDQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_group_t group = dispatch_group_create(); // Add a task to the group dispatch_group_async(group, aDQueue, ^{ printf(task 1 \n); }); dispatch_group_async(group, aDQueue, ^{ printf(task 2 \n); }); dispatch_group_async(group, aDQueue, ^{ printf(task 3 \n); }); printf(wait 1 2 3 \n); dispatch_group_wait(group, DISPATCH_TIME_FOREVER); printf(task 1 2 3 finished \n);dispatch_async 与 dispatch_get_global_queue 分类： IPhone编程 #define kBgQueue dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) - (void)viewDidLoad { [super viewDidLoad]; dispatch_async(kBgQueue, ^{ NSData* data = [NSData dataWithContentsOfURL: kLatestKivaLoansURL]; [self performSelectorOnMainThread:@selector(fetchedData:) withObject:datawaitUntilDone:YES]; }); } dispatch_async会向kBgQueue队列中添加新的任务去执行，这里kBgQueue队列使用dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)获得。 Dispatch Queues Dispatch Queues从使用的角度将更象另一种形式的Operation Queues只是 Operation Queuse是用ObjectC的Dispatch Queues是C的 dispatch Queues有serial Queues 也被称为私有dispatch Queues，一个时间只能运行一个task，顺序运行 dispatch_queue_t queue; queue = dispatch_queue_create(myQueue, NULL); dispatch_async(queue, ^{ printf(Do some work here.\n); }); printf(The first block may or may not have run.\n); dispatch_sync(queue, ^{ printf(Do some more work here.\n); }); printf(Both blocks have completed.\n); 这里使用了同步dispatch和异步dispatch，推荐使用dispatch_async这样才能真正体现其中的优势同步相当于WaitUntil ＝ YES 还有一种就是Concurrent Queues每个程序系统自动提供了3个Concurrent Queues dispatch_queue_t aQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_queue_t aHQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0); dispatch_queue_t aLQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0); 啥意思一看就明白，3个优先级别的concurrent queues 最后一个特殊的Dis