Attempt to present UIAlertController whose view is not in the window hierarchy - Swift Error - ios

Question

I'm trying to create an alert so when a user signs up and then wants to log back in they can be warned if the password is wrong because at the moment it just performs the segue and the attempt to alert fails. I'm using Firebase so the password that is entered into firebase on sign up should be the one users log in with.
import Foundation
import UIKit
import Firebase
class SignInViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var EmailAddressTextField: UITextField!
#IBOutlet weak var PasswordTextField: UITextField!
// Do any additional setup after loading the view.
override func viewDidLoad() {
super.viewDidLoad()
EmailAddressTextField.delegate = self
PasswordTextField.delegate = self
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
}
#IBAction func LogInButton(_ sender: Any) {
if (EmailAddressTextField.text != "" && PasswordTextField.text != ""){
Auth.auth().signIn(withEmail: EmailAddressTextField.text!, password: PasswordTextField.text!) { user, error in
if error == nil {
self.performSegue(withIdentifier: "LogInSegue", sender: nil)
} else {
let alert = UIAlertController(title: "Error", message: "Enter a correct email and password", preferredStyle: .alert)
let action = UIAlertAction(title: "OK", style: .default, handler: nil)
alert.addAction(action)
self.present(alert, animated: true, completion: nil)
}
}
}
}
}

Answer 1

Just want to check something with you, as your description above is a little unclear. When you enter the wrong email/password combination, does your app still perform the "LogInSegue" (as well as failing to show the alert)?
If so, it sounds like you might have connected your segue to the UIButton instead of the UIViewController.
To check this, click on your segue in the Storyboard and see if the UIButton is highlighted.
If it is, then delete this segue and follow the instruction below to connect your new segue from the view controller:

Answer 2

You are presenting UIAlertController on SignInViewController so at that time SignInViewController is not in navigation stack.
So when you are presenting UIAlertController at that time check the self.navigationController?.viewControllers and verify that it is in stack or not.
for eg.
//check before self.presnt...
print(self.navigationController?.viewControllers)
So you need to make sure that when you are presenting a view controller over another view controller that must be in navigation stack otherwise you will get this message in log.
Attempt to present UIAlertController whose view is not in the window hierarchy
Use the following function to show alert over root view controller
func showAlert(title: String, msg: String, actions:[UIAlertAction]?) {
var actions = actions
let alertVC = UIAlertController(title: title, message: msg, preferredStyle: .alert)
if actions == nil {
actions = [UIAlertAction(title: "OK", style: .default, handler: nil)]
}
for action in actions! {
alertVC.addAction(action)
}
if let rootVC = UIApplication.shared.delegate?.window??.rootViewController {
rootVC.present(alertVC, animated: true, completion: nil)
} else {
print("Root view controller is not set.")
}
}
Usage
self.showAlert(title: "My App", msg: "your message", actions: nil)
You need to use this with your code like this...
class SignInViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var EmailAddressTextField: UITextField!
#IBOutlet weak var PasswordTextField: UITextField!
// Do any additional setup after loading the view.
override func viewDidLoad() {
super.viewDidLoad()
EmailAddressTextField.delegate = self
PasswordTextField.delegate = self
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
}
#IBAction func LogInButton(_ sender: Any) {
if (EmailAddressTextField.text != "" && PasswordTextField.text != ""){
Auth.auth().signIn(withEmail: EmailAddressTextField.text!, password: PasswordTextField.text!) { user, error in
if error == nil {
self.performSegue(withIdentifier: "LogInSegue", sender: nil)
} else {
// let alert = UIAlertController(title: "Error", message: "Enter a correct email and password", preferredStyle: .alert)
// let action = UIAlertAction(title: "OK", style: .default, handler: nil)
// alert.addAction(action)
// self.present(alert, animated: true, completion: nil)
//use like this...
self.showAlert(title: "Error", msg: "Enter a correct email and password", actions: nil)
}
}
}
}
//###############################################
func showAlert(title: String, msg: String, actions:[UIAlertAction]?) {
var actions = actions
let alertVC = UIAlertController(title: title, message: msg, preferredStyle: .alert)
if actions == nil {
actions = [UIAlertAction(title: "OK", style: .default, handler: nil)]
}
for action in actions! {
alertVC.addAction(action)
}
if let rootVC = UIApplication.shared.delegate?.window??.rootViewController {
rootVC.present(alertVC, animated: true, completion: nil)
} else {
print("Root view controller is not set.")
}
}
//###############################################
}

Answer 3

Present it in main activity :
dispatch_async(dispatch_get_main_queue(), ^{
let alert = UIAlertController(title: "Error", message: "Enter a correct email and password", preferredStyle: .alert)
let action = UIAlertAction(title: "OK", style: .default, handler: nil)
alert.addAction(action)
self.present(alert, animated: true, completion: nil)
});