短信倒计时

最近发现一个比较好用的短信倒计时，用时直接调下面的方法就行 //验证码倒计时 -(void)startTime{

__block int timeout= 59; //倒计时时间

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); //每秒执行

dispatch_source_set_event_handler(_timer, ^{

    if(timeout<=0){ //倒计时结束，关闭

        dispatch_source_cancel(_timer);

        dispatch_async(dispatch_get_main_queue(), ^{

            //设置界面的按钮显示 根据自己需求设置

            [_codeButton setTitle:@"获取验证码" forState:UIControlStateNormal];

            _codeButton.userInteractionEnabled = YES;

        });

    }else{

        //            int minutes = timeout / 60;

        int seconds = timeout % 60;

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

        dispatch_async(dispatch_get_main_queue(), ^{

            //设置界面的按钮显示 根据自己需求设置

            [UIView beginAnimations:nil context:nil];

            [UIView setAnimationDuration:1];

            [_codeButton setTitle:[NSString stringWithFormat:@"%@秒重发",strTime] forState:UIControlStateNormal];

            [UIView commitAnimations];

            _codeButton.userInteractionEnabled = NO;

        });

        timeout--;

    }

});

dispatch_resume(_timer);