在解除视图之前显示UIAlert

Question

我的视图正在通过导航栏上的上一个按钮被忽略。 我认为正确的术语是视图从视图堆栈中弹出。 在实际解除视图之前，我想显示一个UIAlert，要求用户设置他/她的地址。

我试过这个，但UIAlert没有显示：

override func viewWillDisappear(animated: Bool) {
    if let currentUser = ApiManager.sharedInstance.currentUser {
        if !currentUser.hasAddress {
            let alert = UIAlertController(title: "Missing address", message: "We see you're stilling missing an address, would you like set it now?", preferredStyle: UIAlertControllerStyle.Alert)

            alert.addAction(UIAlertAction(title: "yes".localized, style: .Default, handler: { (alertAction) in
                let newViewController = LocationViewController()
                newViewController.delegate = self
                self.navigationController?.pushViewController(newViewController, animated: true)
            }))

            alert.addAction(UIAlertAction(title: "no".localized, style: .Default, handler: nil))

            self.presentViewController(alert, animated: true, completion: nil)
        }
    }
}

在我的控制台中打印以下内容：

2016-10-28 16:58:47.380 gaifong[17096:14515422] Warning: Attempt to present <UIAlertController: 0x7fd7037e4cb0> on <gaifong.ProfileViewController: 0x7fd7048cc000> whose view is not in the window hierarchy!

Answer 1

您应该添加leftBarButtonItem上navigationItem并作出行动leftBarButtonItem在那里你可以处理这个问题。

在viewDidLoad

self.navigationItem.leftBarButtonItem = UIBarButtonItem(image: image, style: UIBarButtonItemStyle.Plain, target: self, action: #selector(self.goBack))

// Then handle the button selection
func goBack() {
  if let currentUser = ApiManager.sharedInstance.currentUser {
    if !currentUser.hasAddress {
        let alert = UIAlertController(title: "Missing address", message: "We see you're stilling missing an address, would you like set it now?", preferredStyle: UIAlertControllerStyle.Alert)

        alert.addAction(UIAlertAction(title: "yes".localized, style: .Default, handler: { (alertAction) in
            // here you can pop to main controller
            self.navigationController?.popViewControllerAnimated(true)
        }))

        alert.addAction(UIAlertAction(title: "no".localized, style: .Default, handler: nil))

        self.presentViewController(alert, animated: true, completion: nil)
    }
}
}