- (void)yourButtonTitleTime

{

__block int timeout=30; //倒計時時間

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);

    dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒執行

    dispatch_source_set_event_handler(_timer, ^{

        if(timeout<=0){ //倒計時結束，關閉

            dispatch_source_cancel(_timer);

            dispatch_async(dispatch_get_main_queue(), ^{

                //設置界面的按鈕顯示 根據自己需求設置

                [yourbutton setTitle:@"發送驗證碼" forState:UIControlStateNormal];

                yourbutton.userInteractionEnabled = YES;

            });

        }else{

            //            int minutes = timeout / 60;

            int seconds = timeout % 60;

            NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];

            dispatch_async(dispatch_get_main_queue(), ^{

                //設置界面的按鈕顯示 根據自己需求設置

                NSLog(@"____%@",strTime);

                [yourbutton setTitle:[NSString stringWithFormat:@"%@秒后重新發送",strTime] forState:UIControlStateNormal];

                yourbutton.userInteractionEnabled = NO;

            });

            timeout--;

        }

    });

    dispatch_resume(_timer);

}