GCD学习(六) dispatch_async 和dispatch_sync

dispatch_sync(),同步添加操作。他是等待添加进队列里面的操作完成之后再继续执行。

    dispatch_queue_t concurrentQueue = dispatch_queue_create("my.concurrent.queue", DISPATCH_QUEUE_CONCURRENT);
    NSLog(@"1");
    dispatch_sync(concurrentQueue, ^(){
        NSLog(@"2");
        [NSThread sleepForTimeInterval:10];
        NSLog(@"3");
    });
    NSLog(@"4");
输出 ： 
       

11:36:25.313 GCDSeTest[544:303] 1

11:36:25.313 GCDSeTest[544:303] 2

11:36:30.313 GCDSeTest[544:303] 3//模拟长时间操作

11:36:30.314 GCDSeTest[544:303] 4

dispatch_async ,异步添加进任务队列，它不会做任何等待

    dispatch_queue_t concurrentQueue = dispatch_queue_create("my.concurrent.queue", DISPATCH_QUEUE_CONCURRENT);
    NSLog(@"1");
    dispatch_async(concurrentQueue, ^(){
        NSLog(@"2");
        [NSThread sleepForTimeInterval:5];
        NSLog(@"3");
    });
    NSLog(@"4");
输出：

 11:42:43.820 GCDSeTest[568:303] 1

 11:42:43.820 GCDSeTest[568:303] 4

 11:42:43.820 GCDSeTest[568:1003] 2

 11:42:48.821 GCDSeTest[568:1003] 3//模拟长时间操作时间