GoogleAuth using Firebase in IOS

Question

I am following the instructions of the official Firebase channel (https://firebase.google.com/docs/auth/ios/google-signin?hl=en-419) to subscribe into my app using Google authentication. The problem appears in the function

func sign(_ signIn: GIDSignIn!, didSignInFor user: GIDGoogleUser!, withError error: Error?)  

Where it does not resolve the identifiers GoogleAuthProvider and Auth from the commands. i.e. "Use of unresolved identifier 'GoogleAuthProvider'"

let credential = GoogleAuthProvider.credential(idToken: authentication.idToken, accessToken: authentication.accessToken)
        // ...
Auth.auth().signIn(with: credential) { (user, error) in
            if let error = error {
                // ...
                return
            } 

I imported in both the viewer and the AppDelegate:

import Firebase
import GoogleSignIn

And my Podfile looks like that:

# Uncomment the next line to define a global platform for your project
# platform :ios, '9.0'

target 'racc' do
  # Comment the next line if you're not using Swift and don't want to use dynamic frameworks
  use_frameworks!

  # Pods for racc
  pod 'Firebase/Core'
  pod 'GoogleSignIn'
  pod 'Firebase/Auth'

  target 'raccTests' do
    inherit! :search_paths
    # Pods for testing
  end

end

I am working in Swift 4

Answer 1

You need to import FirebaseAuth into your App Delegate.

In your Podfile: pod 'Firebase/Auth'

In your AppDelegate: import FirebaseAuth

These steps are missing from the official Google instructions.

Answer 2

It's most likely that you do not have Google Login enabled in your Firebase Dashboard. To enable, go to the Firebase Dashboard, and click on your project.

From there, tap Authentication, and Sign-In Method. Find Google, and hit Enable.