GCD debug

-(void)gcdTest1
{
    dispatch_queue_t concurrentDispatchQueue=dispatch_queue_create("com.test.queue", DISPATCH_QUEUE_CONCURRENT);
  
    dispatch_async(concurrentDispatchQueue, ^{
        NSLog(@"1");
    });
    dispatch_async(concurrentDispatchQueue, ^{
        sleep(2);
        NSLog(@"2");
    });
    dispatch_async(concurrentDispatchQueue, ^{
        sleep(1);
        NSLog(@"3");
    });
}
// 创建一个并发队列
// 然后异步的去执行
DISPATCH_QUEUE_CONCURRENT + async 才会多个线程
2016-07-21 12:57:48.883 ReactiveCocoaPractice[7139:11438400] 1
2016-07-21 12:57:49.887 ReactiveCocoaPractice[7139:11438411] 3
2016-07-21 12:57:50.888 ReactiveCocoaPractice[7139:11438408] 2

其他实验

各种组合下的输出

DISPATCH_QUEUE_SERIAL + sync
2016-07-21 12:58:43.713 ReactiveCocoaPractice[7213:11440506] 1
2016-07-21 12:58:45.715 ReactiveCocoaPractice[7213:11440506] 2
2016-07-21 12:58:46.716 ReactiveCocoaPractice[7213:11440506] 3

DISPATCH_QUEUE_CONCURRENT + sync
2016-07-21 12:56:33.542 ReactiveCocoaPractice[7013:11434963] 1
2016-07-21 12:56:35.543 ReactiveCocoaPractice[7013:11434963] 2
2016-07-21 12:56:36.544 ReactiveCocoaPractice[7013:11434963] 3

DISPATCH_QUEUE_SERIAL + async
2016-07-21 12:57:20.338 ReactiveCocoaPractice[7090:11437140] 1
2016-07-21 12:57:22.343 ReactiveCocoaPractice[7090:11437140] 2
2016-07-21 12:57:23.347 ReactiveCocoaPractice[7090:11437140] 3

DISPATCH_QUEUE_CONCURRENT + async 才会多个线程
2016-07-21 12:57:48.883 ReactiveCocoaPractice[7139:11438400] 1
2016-07-21 12:57:49.887 ReactiveCocoaPractice[7139:11438411] 3
2016-07-21 12:57:50.888 ReactiveCocoaPractice[7139:11438408] 2