Swift2 加载UIAlertController时出错

我想在internet连接不可用时加载警报。检查internet连接的功能已就绪，但我无法加载警报。因此，我只是在没有任何条件的情况下将警报代码放入viewDidLoad中，并得到以下错误：

警告：尝试在x上显示UIAlertController:0x12752d400。其视图不在窗口层次结构中的ViewController:0x127646f00

代码：

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你能告诉我怎么修吗？

这个错误告诉你出了什么问题

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您试图在

viewdiload

中显示视图控制器，但视图虽然已加载，但不在任何层次结构中。尝试将代码放入

viewdideappeage

方法中，该方法在视图出现在屏幕上后调用，并且位于视图层次结构中

Swift 4更新 我认为这可以帮助您解决您的问题：

override func viewDidLoad() {
    super.viewDidLoad()

    verificationCode.delegate = self

    let alert = UIAlertController(title: "Oops!", message:"This feature isn't available right now", preferredStyle: .alert)
    let delete = UIAlertAction(title: "OK", style: .default) { (_) in }
    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (_) in }
    alert.addAction(cancelAction)
    alert.addAction(delete)

    alert.popoverPresentationController?.sourceView = sender as UIView
    UIApplication.shared.keyWindow?.rootViewController?.present(alert, animated: true, completion: nil)

    if (!Util.isConnectedToNetwork()) {
        self.isConnected = false
    }
}

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将代码从viewDidLoad移动到ViewDidDisplay

override func viewDidAppear(animated: Bool) {
    // Delegates
    verificationCode.delegate = self

    let alert = UIAlertController(title: "Oops!", message:"This feature isn't available right now", preferredStyle: .Alert)
    let action = UIAlertAction(title: "OK", style: .Default) { _ in }
    alert.addAction(action)
    self.presentViewController(alert, animated: true) {}


    if (!Util.isConnectedToNetwork()) {
        self.isConnected = false
    }


}

override func viewDidAppear(animated: Bool) {
    // Delegates
    verificationCode.delegate = self

    let alert = UIAlertController(title: "Oops!", message:"This feature isn't available right now", preferredStyle: .Alert)
    let action = UIAlertAction(title: "OK", style: .Default) { _ in }
    alert.addAction(action)
    self.presentViewController(alert, animated: true) {}


    if (!Util.isConnectedToNetwork()) {
        self.isConnected = false
    }


}