UI 实现多线程方式之四 GCD之自定义并行队列

//第二种：自定义并行队列

dispatch_queue_t concurrentQueue =dispatch_queue_create("concurrent",DISPATCH_QUEUE_CONCURRENT);

//向自定义并行队列中添加任务
dispatch_async(concurrentQueue, ^{

NSLog(@"concurrentQueue第一个任务");
});
dispatch_async(concurrentQueue, ^{

NSLog(@"concurrentQueue第二个任务");
});
dispatch_async(concurrentQueue, ^{

NSLog(@"concurrentQueue第三个任务");
});

//阻塞当前写的第一个参数所对应的队列的任务,必须先执行这个“礁石”任务，才能执行当前队列在这个“礁石任务”后的任务。
dispatch_barrier_async(concurrentQueue, ^{

NSLog(@"concurrentQueue阻塞任务");
});

dispatch_barrier_async(concurrentQueue, ^{

NSLog(@"concurrentQueue第四个任务");
});