ios 中计时器的使用方式

//GCD定时器

    dispatch_source_t timer=dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());

    

    dispatch_source_set_timer(timer, dispatch_time(DISPATCH_TIME_NOW, 15ull*NSEC_PER_SEC), DISPATCH_TIME_FOREVER, 1ull*NSEC_PER_SEC);

    

    dispatch_source_set_event_handler(timer, ^{

        NSLog(@"wakeup");

        dispatch_source_cancel(timer);

    });

    

    dispatch_source_set_cancel_handler(timer, ^{

        NSLog(@"cancel");

        dispatch_release(timer);

    });

    //启动

    dispatch_resume(timer);