有以下*-disPATCH_QUEUE_PRIORITY_HIGH:*-disPATCH_QUEUE_PRIORITY_DEFAULT:多用默认*-disPATCH_QUEUE_PRIORITY_LOW:*-disPATCH_QUEUE_PRIORITY_BACKGROUND:*第二个参数为预留参数,一般为0*/letmyQueue:dispatch_queue_t=dispatch_get_global_queue//用异步的方式运行队列里的任务dispatch_async//-------------