Ios 警报控制器未出现错误！Swift项目

我正在尝试使用swift和firebase在iOS应用程序中更改（编辑）用户电子邮件。 在更改电子邮件功能时，我添加了一些错误，并针对每个错误发出警报

当我模拟并测试错误时，例如，我试图输入无效的电子邮件，错误工作正常！ 但是警报没有出现，它给了我这个错误，如下图所示。

代码如下：

    if EmailAddressTF.text=="" || PasswordTF.text=="" || BusinessNameTF.text==""
    {
        let alert = UIAlertController(title: "Oops!", message:"Make sure to fill in all required textfields", preferredStyle: .Alert)
        alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
        self.presentViewController(alert, animated: true){}
    }

    else {

        if RepasswordTF.text != PasswordTF.text
        {
            let alert = UIAlertController(title: "Oops!", message:"You Entered Different Passwords", preferredStyle: .Alert)
            alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
            self.presentViewController(alert, animated: true){}
        }

        else {

            let ref = Firebase(url: "https://businesswallet.firebaseio.com/")

            let mainpass = NSUserDefaults.standardUserDefaults().objectForKey("password") as? String
            let mainEmail = NSUserDefaults.standardUserDefaults().objectForKey("Email") as? String


            let isEqu = (mainEmail == self.EmailAddressTF.text)
            if(isEqu == true)
            {   }
            else
            {
                ref.changeEmailForUser(mainEmail, password: mainpass, toNewEmail: self.EmailAddressTF.text, withCompletionBlock: { error in

                    if error != nil {

                        if let errorCode = FAuthenticationError(rawValue: error.code) {

                            switch (errorCode) {
                            case .EmailTaken:
                                print("Email taken")
                                let alert = UIAlertController(title: "Oops!", message:"Sorry,Email taken", preferredStyle: .Alert)
                                alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
                                self.presentViewController(alert, animated:true){}

                            case .InvalidEmail:
                                print("invalid email")
                                let alert = UIAlertController(title: "Oops!", message:"invalid email", preferredStyle: .Alert)
                                alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
                               self.presentViewController(alert, animated:true){}


                            case .NetworkError:
                                print("Network Error")
                                let alert = UIAlertController(title: "Oops!", message:"Network error, check your connection", preferredStyle: .Alert)
                                alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
                                self.presentViewController(alert, animated: true){}

                            default:
                                print("Unknown Error")
                                let alert = UIAlertController(title: "Oops!", message:"Unknown Error", preferredStyle: .Alert)
                                alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })
                                self.presentViewController(alert, animated: true){}
                            }
                        }





                    } else {

                        NSUserDefaults.standardUserDefaults().setValue(self.EmailAddressTF.text, forKey: "Email")
                        print("Email changed successfully")

                    }

                })

            } //Big Else

---

我该如何解决这个问题呢？

这是obj-c代码，但您可以轻松地将其转换为swift

- (void)throwAlert
{
    UIWindow* window = [[UIApplication sharedApplication] keyWindow];
        UIAlertController *alert = [UIAlertController
                                    alertControllerWithTitle:@"myTitle"
                                    message:@"myMessage"
                                    preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleCancel handler:^(UIAlertAction * action) {}];

    [alert addAction:defaultAction];
    dispatch_async(dispatch_get_main_queue(), ^{
        if (window.rootViewController.presentedViewController != nil)
        {
            [window.rootViewController.presentedViewController presentViewController:alert animated:YES completion:nil];
        }
        else
        {
            [window.rootViewController presentViewController:alert animated:YES completion:nil];
        }
    });

}

斯威夫特：

func throwAlert()
    {
        let window = UIApplication.sharedApplication().keyWindow

        let alert = UIAlertController(title: "Oops!", message:"You Entered Different Passwords", preferredStyle: .Alert)
        alert.addAction(UIAlertAction(title: "OK", style: .Default) { _ in })

        dispatch_async(dispatch_get_main_queue()) {

            if window.rootViewController?.presentedViewController != nil
            {
                window.rootViewController?.presentedViewController!.presentViewController(alert, animated: true){}
            }
            else
            {
                window.rootViewController!.presentViewController(alert, animated: true){}
            }
        }

    }

---

尝试在主线程中显示警报

dispatch_async(dispatch_get_main_queue()) {
let alertController = UIAlertController(title: head, message: message, preferredStyle: .Alert)
let OKAction = UIAlertAction(title: "OK", style: .Default) { (action:UIAlertAction!) in
print("you have pressed OK button");
}
alertController.addAction(OKAction)

self.presentViewController(alertController, animated: false, completion:nil)
}

---

要添加警报控制器，请在任何帮助器类中添加此全局方法

func popAlertMessageController(VC:(UIViewController), title:(String), message:(String)) {
    let alertController:UIAlertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
    let ok:UIAlertAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) { (action) -> Void in
        alertController.dismissViewControllerAnimated(true, completion: nil)
    }
    alertController.addAction(ok)
    VC.presentViewController(alertController, animated: true, completion: nil)
}

您可以在任何需要警报的地方调用此方法，如下所示：

popAlertMessageController(self, title: "Alert", message: "Your message")

---

这意味着您在错误的视图控制器或视图上显示该警报。听起来您试图从当前未显示的视图控制器显示警报控制器。但视图控制器当前已显示！！我不明白！！这意味着什么？您在另一个控制器上呈现一个视图控制器，但您没有保留对它的引用，因此它只会被情节提要保留，然后当您转到呈现另一个模式（也称为警报）时另一个视图不再在故事板中，由于没有引用而被取消分配，并且由于警报将在其上显示的控制器现在为零，因此它将失败。您也没有在主线程上显示警报。@A'sa Dickens，我现在应该怎么做才能解决这个问题？编译器强迫我在第二个点之前添加感叹号！当在模拟器中测试它时，它给了我以下错误：致命错误：在展开可选值时意外地发现了nil是的…您需要感叹号…这是正确的。但你的控制器显示为零，这就是崩溃发生的原因。你能把你的班级的代码贴在你试图调用此警报的地方吗？哦，请不要，我根本看不懂objective-C。你能用swift给我吗？让我们。让我们。应该在哪里准确地添加这个？在每个你想显示警报的地方。在你的情况下，在每一个

案例中

我都尝试过，它在控制台中给了我同样的错误！