In this article we take a look at how to integrate Google Sign In and Firebase. We will use SwiftUI for this project. The full source code for this project can be found here.

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The app won&amp;#x27;t have much UI this time around, since most of the heavy lifting will be done by Google&amp;#x27;s own log in UI. We will just add a simple &amp;quot;Log in with Google&amp;quot; button on the screen and when its tapped, should take the user to the Google Sign In UI.

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However, let&amp;#x27;s first set up Firebase and Google Sign In:

# 1. Setting up Firebase Project:

Head over to [Firebase.com](http:&amp;#x2F;&amp;#x2F;Firebase.com) and create a new account. Once logged in, create a new project in the Firebase Console.

* Head over to [Firebase.com](http:&amp;#x2F;&amp;#x2F;Firebase.com) and create a new account or log in.
* Create a new project in Firebase Console
* Once a new project is created, click Authentication.
* Select &amp;quot;Get Started&amp;quot; and then make sure you enable &amp;quot;Google Sign In&amp;quot; under sign-in methods.

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Next, we will add our iOS app with the Firebase console. Here is how it goes:

* Head over to &amp;quot;Project Overview&amp;quot; and select &amp;quot;Add iOS App&amp;quot;.
* This will ask you for your iOS app bundle ID. You can get this ID from the Xcode, select your Target &amp;gt; General &amp;gt; Bundle Identifier
* Next, download the configuration file generated at the next step to your computer (GoogleService-Info.plist) - we will simple drag and drop this .plist file in the root folder of our Xcode Project

Next we will need to install Firebase SDK. If you don&amp;#x27;t have Firebase already install then you have one of two ways. You can use CocoaPods or Swift Package Manager. I used Swift Package Manager to install SDK on my Xcode.


Here is how to do this:

* In Xcode go to File &amp;gt; Swift Packages &amp;gt; Add Package Dependency…
* You will see a prompt appear, please add this link there:
  &amp;lt;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;firebase&amp;#x2F;firebase-ios-sdk.git&amp;gt;
* Select the version of Firebase you would like to use. Make sure it&amp;#x27;s the latest one.
* Choose the Firebase products you would like to install.

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# 2. Setting up Google Sign In:

Next, we will install Google Sign in SDK. We can do this in one of two ways by either using CocoaPods or using Swift Package Manager. Let&amp;#x27;s use Swift Package Manager. Here is how:

* In Xcode go to File &amp;gt; Swift Packages &amp;gt; Add Package Dependency…
* You will see a prompt appear, please add this link there:
  &amp;lt;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;google&amp;#x2F;GoogleSignIn-iOS&amp;gt;
* Click Add Package
* &amp;#x5C;

And that&amp;#x27;s it. Now we have both Firebase and Google Sign In SDKs. Next, in Xcode head over to the &amp;#96;GoogleService-Info.plist&amp;#96; file that you just dragged into Xcode. and select the URL in front of &amp;#96;Reverse_Client_ID&amp;#96;. Copy this URL and then do this:

* In the left panel of Xcode, click on the file with name of the your project. This is usually the first file.
* Click the file under &amp;#96;Targets&amp;#96; and then click &amp;#96;Info&amp;#96;
* Expand &amp;#96;URL Types&amp;#96; and click on the plus button to add a new URL type property.
* Paste the &amp;#96;Reverse_Client_ID&amp;#96; in the &amp;#96;URL schemes&amp;#96; text field.

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# Implementation:

Now we are all set with the prerequisites. Now create an &amp;#96;AppDelegate&amp;#96; file and add the following code:

&amp;#96;&amp;#96;&amp;#96;javascript
import UIKit
import Firebase
import GoogleSignIn


class AppDelegate: NSObject, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -&amp;gt; Bool {
        FirebaseApp.configure()
        return true
    }

    func application(_ application: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey: Any]) -&amp;gt; Bool {
      return GIDSignIn.sharedInstance.handle(url)
    }
}
&amp;#96;&amp;#96;&amp;#96;

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First of all, we are just importing the &amp;#96;Firebase&amp;#96; and &amp;#96;GoogleSignIn&amp;#96; modules. Then in &amp;#96;appdidfinishLaunching&amp;#96; method, we are configuring Firebase by adding the code &amp;#96;Firebase.confgure()&amp;#96;. Next, we are going to link Google Sign in by adding another method which returns a &amp;#96;GIDSignIn shared instance&amp;#96;.

In the &amp;#96;.app&amp;#96; file please add the following code in order to link the new &amp;#96;AppDelegate&amp;#96; file:

&amp;#96;&amp;#96;&amp;#96;javascript
@main
struct GoogleSignInFirebaseApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate &amp;#x2F;&amp;#x2F;add this line

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}
&amp;#96;&amp;#96;&amp;#96;

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Now, we just need to implement the Google Sign in call back. Let&amp;#x27;s create a &amp;#96;LoginView.swift&amp;#96; file add the following code:

&amp;#96;&amp;#96;&amp;#96;javascript
struct LoginView: View {
    @AppStorage(&amp;quot;loginStatus&amp;quot;) var loginStatus = false &amp;#x2F;&amp;#x2F;1
    @State var presentSheet: Bool = false &amp;#x2F;&amp;#x2F; 2

    var body: some View {

        
        ZStack {
          &amp;#x2F;&amp;#x2F;Just a simple button when tapped invokes signInWithGoogle method
            Button {
                signInWithGoogle()
            } label: {
                Text(&amp;quot;Log In using Google&amp;quot;)
                    .padding()
                    .background(Color.blue)
                    .cornerRadius(20)
                    .foregroundColor(Color.white)
            }
        }
        &amp;#x2F;&amp;#x2F;Presents HomeView modally
        .fullScreenCover(isPresented: $presentSheet) {
                HomeView()
        }


    }

    &amp;#x2F;&amp;#x2F; The main deal...

    func signInWithGoogle() {
        guard let clientID = FirebaseApp.app()?.options.clientID else { return }

        &amp;#x2F;&amp;#x2F; Create Google Sign In configuration object.
        let config = GIDConfiguration(clientID: clientID)

        &amp;#x2F;&amp;#x2F; Start the sign in flow!
        GIDSignIn.sharedInstance.signIn(with: config, presenting: getRootViewController()) {  user, error in

          if let error = error {
            print(error)
            return
          }

          guard let authentication = user?.authentication,
                let idToken = authentication.idToken
          else {
            return
          }

          let credential = GoogleAuthProvider.credential(withIDToken: idToken,
                                                         accessToken: authentication.accessToken)

            Auth.auth().signIn(with: credential) { result, err in
                if let err = error {
                  print(err)
                  return
                }

                guard let user = result?.user else { return }

                print(user.displayName ?? &amp;quot;Success!&amp;quot;)
                self.presentSheet = true
                withAnimation {
                    self.loginStatus = true
                }

            }
        }
    }

}
&amp;#96;&amp;#96;&amp;#96;

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Let&amp;#x27;s go over in detail what is going on in &amp;#96;signInWithGoogle()&amp;#96; method. Initially, we are getting the &amp;#96;client ID&amp;#96; from Firebase, and then creating a Google Sign In &amp;#96;configuration&amp;#96; object using the &amp;#96;clientID&amp;#96;. Then once we have that we will start the sign in flow. We call the &amp;#96;GIDSignIn.sharedInstance.signIn&amp;#96; method which takes in the &amp;#96;configuration&amp;#96; object, and the root view controller. To extract the &amp;#96;rootViewController&amp;#96; please use the following extension on &amp;#96;View&amp;#96;:

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&amp;#96;&amp;#96;&amp;#96;javascript
extension View {
    func getRootViewController() -&amp;gt; UIViewController {
        guard let screen = UIApplication.shared.connectedScenes.first as? UIWindowScene else {
            return .init()
        }

        guard let root = screen.windows.first?.rootViewController else {
            return .init()
        }

        return root

    }
}
&amp;#96;&amp;#96;&amp;#96;

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The &amp;#96;GIDSignIn&amp;#96; method requires &amp;#96;rootViewController&amp;#96; so that it can present it&amp;#x27;s own view controller which presents the Google Sign In UI. Once the user signs in to the Google account and is successful in doing so, the callback returns with &amp;#96;error&amp;#96; and &amp;#96;result&amp;#96;. If there is no error present, we get user object with authentication id token. We use this authorization id token to create a credential. We will now use this credential to create a new user and sign into Firebase authentication using &amp;#96;Auth.auth().signin()&amp;#96; method. This method returns an error and result. If there is no error, we can get the user from the result object and toggle &amp;#96;presentSheet&amp;#96; boolean to true which will show the &amp;#96;HomeView&amp;#96;.

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Also, here we are using &amp;#96;@AppStorage&amp;#96; property wrapper which acts like &amp;#96;UserDefaults&amp;#96; and saves the state of the user. So since we just signed in successfully to Firebase using Google Sign in, we will make &amp;#96;loginStatus&amp;#96; which is an &amp;#96;@AppStorage&amp;#96; variable to &amp;#96;true&amp;#96;. We will use this to do login persistence. 

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Now, in &amp;#96;HomeView.swift&amp;#96; file, lets add the following code:

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&amp;#96;&amp;#96;&amp;#96;javascript
import SwiftUI
import Firebase
import GoogleSignIn

struct User {
    var id: String = &amp;quot;&amp;quot;
    var name: String = &amp;quot;&amp;quot;
    var email: String = &amp;quot;&amp;quot;

}

struct HomeView: View {
    @State var user = User()
    @AppStorage(&amp;quot;loginStatus&amp;quot;) var loginStatus = false
    var body: some View {
        VStack(spacing: 20) {
            Text(&amp;quot;Welcome,&amp;#x5C;(user.name)&amp;quot;)
                .onAppear {
                    guard let user = Auth.auth().currentUser else { return }
                    self.user = User(id: user.uid, name: user.displayName ?? &amp;quot;&amp;quot;, email: user.email ?? &amp;quot;&amp;quot;)
            }

            Button {
                GIDSignIn.sharedInstance.signOut()
                try? Auth.auth().signOut()

                withAnimation {
                    self.loginStatus = false
                }
            } label: {
                Text(&amp;quot;Log Out&amp;quot;)
            }

        }
    }
}
&amp;#96;&amp;#96;&amp;#96;

&amp;#x5C;
Here, we when the view appears, we are using the Firebase&amp;#x27;s &amp;#96;currentUser&amp;#96; method to get the logged in user info and then creating a &amp;#96;User&amp;#96; object and then showing the &amp;#96;user.displayName&amp;#96; in the &amp;#96;Text&amp;#96; view. Also we have implemented a Log Out button which when pressed simply logs out the user from Google and Firebase. And observe, that we again changing the &amp;#96;loginStatus&amp;#96; variable to &amp;#96;false&amp;#96;.

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Now, in the &amp;#96;ContentView.swift&amp;#96; file add the following code:

&amp;#96;&amp;#96;&amp;#96;javascript
struct ContentView: View {
    @AppStorage(&amp;quot;loginStatus&amp;quot;) var loginStatus = false
    var body: some View {
        if loginStatus {
            HomeView()
        }else {
            LoginView()
        }

    }
}
&amp;#96;&amp;#96;&amp;#96;

&amp;#x5C;
We are checking the &amp;#96;loginStatus&amp;#96;, and if it is &amp;#96;false&amp;#96;, then we show the &amp;#96;LogInView&amp;#96; else we show the &amp;#96;HomeView&amp;#96;.

You can refer to our [Firebase Authentication with Email and Password](https:&amp;#x2F;&amp;#x2F;dopebase.com&amp;#x2F;firebase-swiftui) tutorial to know more about how to save  User’s data (name, email, id) in a &amp;#96;Firestore&amp;#96; database and then retrieving it by using &amp;#96;user.uid&amp;#96; to query the database.

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Google Sign In and Firebase Authentication using SwiftUI

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