在关闭之前的 AlertViewController 后呈现新的 AlertViewController - Swift

我试图在用户选择第一个 AlertViewController 中的操作后呈现新警报。请在下面找到我的代码。

@IBAction func forgotPassword(sender : AnyObject){

    //1. Create the alert controller.
    let alert = UIAlertController(title: "Forgot Password?", message: "We'll email a link to reset it.", preferredStyle: .Alert)

    //2. Add the text field. You can configure it however you need.
    alert.addTextFieldWithConfigurationHandler({ (textField) -> Void in
        textField.placeholder = "Email Address"
    })

    //3. Grab the value from the text field, and print it when the user clicks OK.
    alert.addAction(UIAlertAction(title: "Send", style: .Default, handler: { (action) -> Void in
        let textField = alert.textFields![0] as UITextField
        let email = textField.text!
        FIRAuth.auth()?.sendPasswordResetWithEmail(email) { error in
            if error != nil {
                // An error happened.
            } else {
                print("error is nil")
                if self.presentedViewController != nil {
                    self.presentedViewController?.dismissViewControllerAnimated(true, completion: {
                    print("inside completion")
                    let alertController = UIAlertController(title: "Email Sent!", message: "Please check you email and follow the password reset instructions", preferredStyle: .Alert)
                    let action = UIAlertAction(title: "Done", style: .Default, handler: nil)
                    alertController.addAction(action)
                    self.presentViewController(alertController, animated: true, completion: nil)     
                   })
               }
         }
    }
}))
     // 4. Present the alert.
        self.presentViewController(alert, animated: true, completion: nil)
}

无论我在完成块中编写什么代码，它都不会被执行，因此第二个警报不会显示。请帮我解决这个问题。

UIAlertView 似乎会在执行操作后自行关闭。

//3. Grab the value from the text field, and print it when the user clicks OK.
alert.addAction(UIAlertAction(title: "Send", style: .Default, handler: { (action) -> Void in
    let textField = alert.textFields![0] as UITextField

    guard let email = textField.text else {
        return
    }

    FIRAuth.auth()?.sendPasswordResetWithEmail(email) { error in
        if let error = error {
            print(error.localizedDescription)
            return
        }

        let alertController = UIAlertController(title: "Email Sent!", message: "Please check you email and follow the password reset instructions", preferredStyle: .Alert)
        let action = UIAlertAction(title: "Done", style: .Default, handler: nil)
        alertController.addAction(action)
        self.presentViewController(alertController, animated: true, completion: nil)

    }
}))