GCD学习(五) dispatch_barrier_async
2015-04-03 15:47
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先看段代码
dispatch_barrier_async 作用是在并行队列中,等待前面两个操作并行操作完成,这里是并行输出
dispatch-1,dispatch-2
然后执行
dispatch_barrier_async中的操作,(现在就只会执行这一个操作)执行完成后,即输出
"dispatch-barrier,
最后该并行队列恢复原有执行状态,继续并行执行
dispatch-3,dispatch-4
dispatch_queue_t concurrentQueue = dispatch_queue_create("my.concurrent.queue", DISPATCH_QUEUE_CONCURRENT); dispatch_async(concurrentQueue, ^(){ NSLog(@"dispatch-1"); }); dispatch_async(concurrentQueue, ^(){ NSLog(@"dispatch-2"); }); dispatch_barrier_async(concurrentQueue, ^(){ NSLog(@"dispatch-barrier"); }); dispatch_async(concurrentQueue, ^(){ NSLog(@"dispatch-3"); }); dispatch_async(concurrentQueue, ^(){ NSLog(@"dispatch-4"); });
dispatch_barrier_async 作用是在并行队列中,等待前面两个操作并行操作完成,这里是并行输出
dispatch-1,dispatch-2
然后执行
dispatch_barrier_async中的操作,(现在就只会执行这一个操作)执行完成后,即输出
"dispatch-barrier,
最后该并行队列恢复原有执行状态,继续并行执行
dispatch-3,dispatch-4
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