dispatch_set_target_queue测试
dispatch_set_target_queue会将其他queue转为和targetqueue一样的优先级和执行时序,看下面的例子
即使queue1,queue2,queue3,都是并行的queue,但是输出结果仍然是串行的结果;
- (void)testTargetQueue { dispatch_queue_t targetQueue = dispatch_queue_create("test.target.queue", DISPATCH_QUEUE_SERIAL); dispatch_queue_t queue1 = dispatch_queue_create("test.1", DISPATCH_QUEUE_CONCURRENT); dispatch_queue_t queue2 = dispatch_queue_create("test.2", DISPATCH_QUEUE_CONCURRENT); dispatch_queue_t queue3 = dispatch_queue_create("test.3", DISPATCH_QUEUE_CONCURRENT); dispatch_set_target_queue(queue1, targetQueue); dispatch_set_target_queue(queue2, targetQueue); dispatch_set_target_queue(queue3, targetQueue); dispatch_async(queue1, ^{ NSLog(@"1 in"); [NSThread sleepForTimeInterval:3.f]; NSLog(@"1 out"); }); dispatch_async(queue2, ^{ NSLog(@"2 in"); [NSThread sleepForTimeInterval:2.f]; NSLog(@"2 out"); }); dispatch_async(queue3, ^{ NSLog(@"3 in"); [NSThread sleepForTimeInterval:1.f]; NSLog(@"3 out"); }); }
2017-03-07 20:31:11.636 DispatchTargetQueueTest[42985:377250] 1 in
2017-03-07 20:31:14.711 DispatchTargetQueueTest[42985:377250] 1 out
2017-03-07 20:31:14.711 DispatchTargetQueueTest[42985:377250] 2 in
2017-03-07 20:31:16.784 DispatchTargetQueueTest[42985:377250] 2 out
2017-03-07 20:31:16.784 DispatchTargetQueueTest[42985:377250] 3 in
2017-03-07 20:31:17.859 DispatchTargetQueueTest[42985:377250] 3 out