How to show alerts in Swift UIKit using MVVM, Firebase and Delegates - swift

Question

I would like to know how can i implement a delegate or a function that helps me to show an alert in the ViewModel. Basically i need to validate two text fields and when the user writes a wrong password or a wrong email it should trigger an alert. The function to trigger this alert is inside of the ViewController and i need to create a new class (ViewModel) that helps me to validate the text fields and sign to firebase
Here is my code:
ViewController
import UIKit
import FirebaseAuth
class ViewController: UIViewController, UIWindowSceneDelegate {
//MARK: - #IBOutlets
#IBOutlet weak var emailTextField: UITextField!
#IBOutlet weak var passwordTextField: UITextField!
#IBOutlet weak var startButton: UIButton!
//MARK: - LifeCycle
override func viewDidLoad() {
super.viewDidLoad()
setDelegates()
startButton.isEnabled = false
}
//MARK: - Delegates
func setDelegates()->Void {
emailTextField.delegate = self
passwordTextField.delegate = self
}
// Function that i need to trigger in the ViewModel
fileprivate func showErrorMessage(_ errorMessage : String) {
let alertController = UIAlertController(title: "UPS!", message: errorMessage, preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: "Aceptar", style: .default))
self.present(alertController, animated: true, completion: nil)
}
// Function to go to the next ViewController
fileprivate func navigateToHomeViewController() {
let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
let homeViewController = storyBoard.instantiateViewController(withIdentifier: "HomeViewController") as! HomeViewController
homeViewController.modalPresentationStyle = .fullScreen
self.present(homeViewController, animated: true, completion: nil)
}
// Function of the ViewModel all validations
fileprivate func validateUserLogin(_ error: Error?, _ result: AuthDataResult?) {
switch error {
case .some(let error as NSError) where error.code == AuthErrorCode.wrongPassword.rawValue:
// validate the text field and then show the alert, i need to this, but inside the ViewModel
self.showErrorMessage("Contraseña incorrecta")
case .some(let error as NSError) where error.code == AuthErrorCode.userNotFound.rawValue:
// validate the text field and then show the alert, i need to this, but inside the ViewModel
self.showErrorMessage("Correo incorrecto")
case .some(let error):
// validate the text field and then show the alert, i need to this, but inside the ViewModel
self.showErrorMessage("Login error: \(error.localizedDescription)")
self.hideActivityIndicatorView()
case .none:
if (result?.user) != nil {
navigateToHomeViewController()
}
}
}
#IBAction func startButtonAction(_ sender: Any) {
if let email = emailTextField.text, let password = passwordTextField.text{
// Function to sing in firebase, it would be inside the ViewModel
Auth.auth().signIn(withEmail: email, password: password){(result, error) in
self.validateUserLogin(error, result)
}
}
}
fileprivate func validateFields() -> Bool {
return (passwordTextField.text!.count >= 8) && (isValidEmail(emailTextField.text ?? ""))
}
fileprivate func updateView() {
if(validateFields()){
startButton.isEnabled = true
startButton.tintColor = UIColor.blue
}else{
startButton.isEnabled = false
startButton.tintColor = UIColor.gray
}
}
}
func isValidEmail(_ email: String) -> Bool {
let emailRegEx = "[A-Z0-9a-z._%+-]+#[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
let emailPred = NSPredicate(format:"SELF MATCHES %#", emailRegEx)
return emailPred.evaluate(with: email)
}
//MARK: - Text Field Delegate Methods
extension ViewController : UITextFieldDelegate{
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString
string: String) -> Bool {
if textField == self.emailTextField {
updateView()
} else if textField == self.passwordTextField {
updateView()
}
return true
}
}
StoryBoard

Answer 1

Here is the solution, thanks to Not Bad.
Model
import Foundation
struct User{
var email : String
var password : String
}
ViewModel
import Foundation
import FirebaseAuth
class AuthViewModel {
var delegate: AuthViewModelDelegate?
var user : User? = User(email: "", password: "")
func checkCredentials(user: User) {
Auth.auth().signIn(withEmail: user.email, password: user.password){(result, error) in
switch error {
case .some(let error as NSError) where error.code == AuthErrorCode.wrongPassword.rawValue:
self.delegate?.showError("Contraseña incorrecta")
self.delegate?.hideActivityIndicator()
case .some(let error as NSError) where error.code == AuthErrorCode.userNotFound.rawValue:
self.delegate?.showError("Correo incorrecto")
self.delegate?.hideActivityIndicator()
case .some(let error):
self.delegate?.showError("Login error: \(error.localizedDescription)")
self.delegate?.hideActivityIndicator()
case .none:
if (result?.user) != nil {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let homeViewController = storyboard.instantiateViewController(identifier: "HomeViewController")
self.delegate?.navigateToHomeViewController(homeViewController)
self.delegate?.hideActivityIndicator()
}
}
}
}
}
View
import UIKit
import FirebaseAuth
//MARK: - # protocols
protocol AuthViewModelDelegate {
func showError(_ message: String)
func hideActivityIndicator()
func navigateToHomeViewController(_ homeViewController: UIViewController)
}
class ViewController: UIViewController {
//MARK: - #IBOutlets
#IBOutlet weak var emailTextField: UITextField!
#IBOutlet weak var passwordTextField: UITextField!
#IBOutlet weak var startButton: UIButton!
//MARK: - # Variables
var activityIndicator:UIActivityIndicatorView!
var authViewModel : AuthViewModel = AuthViewModel()
//MARK: - # Life cycle
override func viewDidLoad() {
super.viewDidLoad()
setDelegates()
setupUI()
}
fileprivate func setupUI() {
setActivityIndicator()
startButton.isEnabled = false
}
func setDelegates()->Void {
authViewModel.delegate = self
emailTextField.delegate = self
passwordTextField.delegate = self
}
func setActivityIndicator()->Void{
activityIndicator = UIActivityIndicatorView(style: UIActivityIndicatorView.Style.medium)
activityIndicator.center = view.center
activityIndicator.isHidden = true
self.view.addSubview(activityIndicator)
}
func displayActivityIndicatorView() -> () {
self.view.isUserInteractionEnabled = false
self.view.bringSubviewToFront(self.activityIndicator)
self.activityIndicator.isHidden = false
self.activityIndicator.startAnimating()
}
#IBAction func startButtonAction(_ sender: Any) {
self.displayActivityIndicatorView()
guard let email = emailTextField.text else {return}
guard let password = passwordTextField.text else {return}
self.authViewModel.user?.email = email
self.authViewModel.user?.password = password
self.authViewModel.checkCredentials(user: self.authViewModel.user!)
}
fileprivate func validateFields() -> Bool {
return (passwordTextField.text!.count >= 8) && (isValidEmail(emailTextField.text ?? ""))
}
fileprivate func updateView() {
if(validateFields()){
startButton.isEnabled = true
}else{
startButton.isEnabled = false
}
}
}
func isValidEmail(_ email: String) -> Bool {
let emailRegEx = "[A-Z0-9a-z._%+-]+#[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
let emailPred = NSPredicate(format:"SELF MATCHES %#", emailRegEx)
return emailPred.evaluate(with: email)
}
//MARK: - Text Field Delegate Methods
extension ViewController : UITextFieldDelegate{
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString
string: String) -> Bool {
if textField == self.emailTextField {
updateView()
} else if textField == self.passwordTextField {
updateView()
}
return true
}
}
//MARK: - # AuthViewModel Delegate Methods
extension ViewController : AuthViewModelDelegate{
func hideActivityIndicator() {
DispatchQueue.main.async {
if !self.activityIndicator.isHidden{
DispatchQueue.main.async {
self.view.isUserInteractionEnabled = true
self.activityIndicator.stopAnimating()
self.activityIndicator.isHidden = true
}
}
}
}
func navigateToHomeViewController(_ homeViewController: UIViewController) {
(UIApplication.shared.connectedScenes.first?.delegate as? SceneDelegate)?.changeRootViewController(homeViewController)
}
func showError(_ message: String) {
DispatchQueue.main.async {
let alertController = UIAlertController(title: "UPS!", message: message, preferredStyle: .alert)
alertController.addAction(UIAlertAction(title: "Aceptar", style: .default))
self.present(alertController, animated: true, completion: nil)
}
}
}