我有方法：

private static func rootViewController() -> UIViewController {
    // cheating,I know
 
    return UIApplication.shared.keyWindow!.rootViewController!
}
 
static func presentAlert(_ message: String) {
    let alertView = UIAlertController(title: "RxExample",message: message,preferredStyle: .alert)
    alertView.addAction(UIAlertAction(title: "OK",style: .cancel) { _ in })
 
    rootViewController().present(alertView,animated: true,completion: nil)
}

Full code of this class you can find here

我在viewDidLoad中调用presentAlert方法：

override func viewDidLoad() {
    super.viewDidLoad()
    DefaultWireframe.presentAlert("test")
    ...
}

并得到警告：

Warning: Attempt to present UIAlertController: 0x7f904ac0d930 on UIViewController: 0x7f904ad08040 whose view is not in the window hierarchy!

如何避免警告并显示警报？

它在我尝试在初始ViewController中显示Alert时有效,但它在使用push segue与初始VC连接的另一个ViewController中不起作用.