uint64_tinterval =2*NSEC_PER_SEC;
//创建一个专门执行timer回调的GCD队列
dispatch_queue_tqueue =dispatch_queue_create("my queue",0);
//创建Timer
_timer=dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,0,0, queue);
//使用dispatch_source_set_timer函数设置timer参数
dispatch_source_set_timer(_timer,dispatch_time(DISPATCH_TIME_NOW,0), interval,0);
//设置回调
dispatch_source_set_event_handler(_timer, ^()
{
NSLog(@"Timer %@", [NSThreadcurrentThread]);
});
//dispatch_source默认是Suspended状态，通过dispatch_resume函数开始它
dispatch_resume(_timer);
