IOS 的验证码倒计时

-(void)clicksendVerificationCode:(UIButton *)btn{

    __block int timeout = 30;

    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(), ^{

                // 设置界面按钮的显示

                [btn setTitle:@"发送验证码" forState:UIControlStateNormal];

                btn.userInteractionEnabled = YES;

            });

        }else {

            

            int seconds = timeout % 60;

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

            dispatch_async(dispatch_get_main_queue(), ^{

                // 设置界面按钮显示

                [UIView beginAnimations:nil context:nil];

                [UIView setAnimationDuration:1];

                [btn setTitle:[NSString stringWithFormat:@"%@秒后重发",strTime] forState:UIControlStateNormal];

                [UIView commitAnimations];

                btn.userInteractionEnabled = NO;

            });

            timeout--;

        }

    });

    dispatch_resume(_timer);

}

 －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－

NSTimer *timer;
    int time;

// 发送验证码事件
- (void)sendVerify{
    
    time = 60;
    self.verifyBtn.enabled = NO;
    [timer invalidate];
    timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(Countdown) userInfo:nil repeats:YES];
    
}
- (void)Countdown{
    
    time--;
    [self.verifyBtn setTitle:[NSString stringWithFormat:@"重新发送(%d)",time] forState:UIControlStateDisabled];
    if (time == 0) {
        [timer invalidate];
        self.verifyBtn.enabled = YES;
        [self.verifyBtn setTitle:[NSString stringWithFormat:@"获取验证码"] forState:UIControlStateNormal];
    }
}