iOS 验证码倒计时验证码60s（连续快速点击

#pragma mark -  验证码倒计时验证码60s（连续快速点击）
/** 验证码倒计时UI绘制 */
- (void)drawVerifyCodeCountdownUI:(UIButton *)sender {
    __block int timeout = 60; //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
                [sender setTitle:@"重新获取" forState:UIControlStateNormal];
                sender.userInteractionEnabled = YES;
//                sender.backgroundColor = [UIColor colorWithWhite:0.3 alpha:0.5];
            });
        } else {
            int seconds = timeout;
            NSString *strTime = [NSString stringWithFormat:@"%d", seconds];
            dispatch_async(dispatch_get_main_queue(), ^{
                //让按钮变为不可点击的灰色
//                sender.backgroundColor = [UIColor grayColor];
                sender.userInteractionEnabled = NO;
                //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];
                [sender setTitle:[NSString stringWithFormat:@"%@s",strTime] forState:UIControlStateNormal];
                [UIView commitAnimations];
            });
            timeout--;
        }
    });
    dispatch_resume(_timer);
}