iOS开发 - 数字快速变化到指定数字

- (void)countJumpAction
{
    __block int _numText = 0;
    //全局队列    默认优先级
    dispatch_queue_t quene = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    //定时器模式  事件源
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, quene);
    //NSEC_PER_SEC是秒，＊1是每秒
    dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), NSEC_PER_SEC * 0.00003, 0);
    //设置响应dispatch源事件的block，在dispatch源指定的队列上运行
    dispatch_source_set_event_handler(timer, ^{
        //回调主线程，在主线程中操作UI
        dispatch_async(dispatch_get_main_queue(), ^{
            if (_numText <= 9999) {
                _countJump.text = [NSString stringWithFormat:@"%.5d",_numText];
                _numText++;
            }
            else
            {
                //这句话必须写否则会出问题
                dispatch_source_cancel(timer);
                _countJump.text = @"98461";
            }
        });
    });
    //启动源
    dispatch_resume(timer);
}