UIAlertView带有no按钮，怎么关闭

应用中有一个alertView，在服务器返回响应时使用。在应用向服务器发送数据之后，alertView会显示，但是应该怎么关闭呢？

摘抄的部分代码：

   UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Canceling reservation" message:@"please wait" delegate:self cancelButtonTitle:nil otherButtonTitles: nil];
        [alert show];

        UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];

        // Adjust the indicator to place at the bottom of the dialog window.
        indicator.center = CGPointMake(alert.bounds.size.width / 2, alert.bounds.size.height-50);
        [indicator startAnimating];
        [alert addSubview:indicator];