Unable to Connect Sign In with Apple to Firebase

Question

When I connect Sign In with Apple to Firebase it comes up with an Error message 'Cannot assign value of type 'LoginPopupViewController' to type 'ASAuthorizationControllerPresentationContextProviding?' It won't show any users as logged in on the Firebase Console.

I followed the second part of this tutorial: https://www.youtube.com/watch?v=BxQsdhglZtE

import Foundation
import UIKit
import AuthenticationServices
import FirebaseAuth
import Firebase
import FirebaseFirestore
import CryptoKit

class LoginPopupViewController: UIViewController, ASAuthorizationControllerDelegate {
    
    @IBAction func doneBtn(_ sender: Any) {
        dismiss(animated: true, completion: nil)
    }


    override func viewDidLoad() {
        super.viewDidLoad()

        setupSignInButton()
    }

    func setupSignInButton() {
        let button = ASAuthorizationAppleIDButton(type: .signIn, style: .white)
        button.addTarget(self, action: #selector(handleSignInWithAppleTapped), for: .touchUpInside)
        button.frame.size = CGSize(width: 300.0, height: 40.0)
        button.center = view.center
        view.addSubview(button)
    }

    @objc func handleSignInWithAppleTapped() {
        performSignIn()
    }

    func performSignIn() {
        let request = createAppleIDRequest()
        let authorizationController = ASAuthorizationController(authorizationRequests: [request])
        authorizationController.delegate = self
        authorizationController.presentationContextProvider = self
        authorizationController.performRequests()
    }

    func createAppleIDRequest() -> ASAuthorizationOpenIDRequest {
        let appleIDProvider = ASAuthorizationAppleIDProvider()
        let request = appleIDProvider.createRequest()
        request.requestedScopes = [.fullName, .email]

        let nonce = randomNonceString()
        request.nonce = sha256(nonce)
        currentNonce = nonce
        return request
    }
}

extension ViewController: ASAuthorizationControllerDelegate {
    func authorizationController(controller: ASAuthorizationController, didCompleteWithAuthorization authorization: ASAuthorization) {
        if let appleIDCredential = authorization.credential as? ASAuthorizationAppleIDCredential {
            guard let nonce = currentNonce else {
                fatalError("Invalid state: A login callback was recieved, but no login request was sent")
            }
            guard let appleIDToken = appleIDCredential.identityToken else {
                print("Unable to fetch identify token")
                return
            }
            guard let idTokenString = String(data: appleIDToken, encoding: .utf8) else {
                print("Unable to serialize token string from data: \(appleIDToken.debugDescription)")
            return
            }

                let credential = OAuthProvider.credential(withProviderID: "apple.com", idToken: idTokenString, rawNonce: nonce)

                    Auth.auth().signIn(with: credential) { (authDataResult, error) in
                    if let user = authDataResult?.user {
                    print("Nice! You're now signed in as \(user.uid), email: \(user.email ?? "unknown")")
                    }
            }
        }
    }
}

extension ViewController: ASAuthorizationControllerPresentationContextProviding {
    func presentationAnchor(for controller: ASAuthorizationController) -> ASPresentationAnchor {
        return self.view.window!
    }
}



    // Adapted from https://auth0.com/docs/api-auth/tutorials/nonce#generate-a-cryptographically-random-nonce
    private func randomNonceString(length: Int = 32) -> String {
      precondition(length > 0)
      let charset: Array<Character> =
          Array("0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._")
      var result = ""
      var remainingLength = length

      while remainingLength > 0 {
        let randoms: [UInt8] = (0 ..< 16).map { _ in
          var random: UInt8 = 0
          let errorCode = SecRandomCopyBytes(kSecRandomDefault, 1, &random)
          if errorCode != errSecSuccess {
            fatalError("Unable to generate nonce. SecRandomCopyBytes failed with OSStatus \(errorCode)")
          }
          return random
        }

        randoms.forEach { random in
          if remainingLength == 0 {
            return
          }

          if random < charset.count {
            result.append(charset[Int(random)])
            remainingLength -= 1
          }
        }
      }

      return result
    }


    // Unhashed nonce.
    fileprivate var currentNonce: String?

    @available(iOS 13, *)
    private func sha256(_ input: String) -> String {
      let inputData = Data(input.utf8)
      let hashedData = SHA256.hash(data: inputData)
      let hashString = hashedData.compactMap {
        return String(format: "%02x", $0)
      }.joined()

      return hashString
    }

Answer 1

You need LoginPopupViewController to conform to ASAuthorizationControllerPresentationContextProviding

extension LoginPopupViewController: ASAuthorizationControllerPresentationContextProviding {
    func presentationAnchor(for controller: ASAuthorizationController) -> ASPresentationAnchor {
        return self.view.window!
    }
}