短信倒计时

//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);
}

- (void)getCodeAction:(UIButton *)sender {
     // 解决按钮短时间内多次点击只触发一次事件方法
    [[self class] cancelPreviousPerformRequestsWithTarget:self selector:@selector(startTime) object:_codeButton];
    [self performSelector:@selector(startTime) withObject:_codeButton afterDelay:0.2f];
}