xcode7 弹出提醒等简单窗口
最简单方法
UIAlertView(title: “提醒”, message:”登陆失败，请确认账号和密码信息”, delegate: nil, cancelButtonTitle: “确定”).show()

如弹出窗口还有其他操作。

func showAlert(){
        let alertController = UIAlertController(title: "系统提示",
            message: "账号错误", preferredStyle: UIAlertControllerStyle.Alert)
        let tryAction = UIAlertAction(title: "继续重试", style: UIAlertActionStyle.Cancel, handler: nil)
        let exitAction = UIAlertAction(title: "退出", style: UIAlertActionStyle.Default,
            handler: {
                ACTION in exit(0)
        })
        alertController.addAction(tryAction)
        alertController.addAction(exitAction)
        self.presentViewController(alertController, animated: true, completion: nil)
}