Add sign-in to SwiftUI iOS app with FirebaseUI.

SignInView.swift

import SwiftUI
import FirebaseUI

struct SignInView: View {
    @State private var user: FirebaseAuth.User?

    var body: some View {
        SignInViewController(user: $user)
    }
}

struct SignInView_Previews: PreviewProvider {
    static var previews: some View {
        SignInView()
    }
}

struct SignInViewController: UIViewControllerRepresentable {
    @Binding var user: FirebaseAuth.User?

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIViewController(context: Context) -> _SignInViewController {
        return _SignInViewController.makeInstance(delegate: context.coordinator)
    }

    func updateUIViewController(_ uiViewController: _SignInViewController, context: Context) {}

    class Coordinator: NSObject, FUIAuthDelegate {
        var parent: SignInViewController

        init(_ viewController: SignInViewController) {
            self.parent = viewController
        }

        func authUI(_ authUI: FUIAuth, didSignInWith authDataResult: AuthDataResult?, error: Error?) {
            parent.user = authDataResult?.user
        }
    }
}

final class _SignInViewController: UIViewController {
    private let authUI = FUIAuth.defaultAuthUI()!

    static func makeInstance(delegate: FUIAuthDelegate) -> _SignInViewController {
        let vc = R.storyboard.signIn.signInViewController()!
        vc.authUI.delegate = delegate
        return vc
    }

    @IBAction func didTapSignInButton(_ sender: Any) {
        authUI.providers = [FUIPhoneAuth(authUI: authUI)]
        let provider = authUI.providers.first as! FUIPhoneAuth
        provider.signIn(withPresenting: self, phoneNumber: nil)
    }
}

let vc = R.storyboard.signIn.signInViewController()!

I am new to Swift and apple dev. What is R? I created a swift view with your code but Xcode does not know what R is and either do I. A little help please!

It's code using R.swift 😄