How to use FirebaseUI for Google authentication on iOS in Swift?

Question

I'm following https://firebase.google.com/docs/auth/ and want to use FirebaseUI (https://github.com/firebase/FirebaseUI-iOS/tree/master/FirebaseUI) for authentication.

The UI shows successfully and I'm able to click "sign in with google" and then complete the web sign in flow. The app re-opens with the auth url, but the authUI function never fires. What's wrong?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.
    FIRApp.configure()

    let authUI = FIRAuthUI.authUI()!;
    NSLog("setting up delegate");
    authUI.delegate = self;

    let googleAuthUI = FIRGoogleAuthUI.init(clientID:FIRApp.defaultApp()!.options.clientID);

    authUI.signInProviders = [googleAuthUI!];


    mSplitViewController = self.window!.rootViewController as! UISplitViewController


    self.window!.rootViewController = authUI.authViewController();

    return true
}

    func authUI(authUI: FIRAuthUI, didSignInWithUser user: FIRUser?, error:NSError?) {
    // Implement this method to handle signed in user or error if any.
    NSLog("logged in");

    self.window!.rootViewController = mSplitViewController
    let navigationController = mSplitViewController!.viewControllers[mSplitViewController!.viewControllers.count-1] as! UINavigationController

    navigationController.topViewController!.navigationItem.leftBarButtonItem = mSplitViewController!.displayModeButtonItem()
    mSplitViewController!.delegate = self

    let masterNavigationController = mSplitViewController!
        .viewControllers[0] as! UINavigationController
    let controller = masterNavigationController.topViewController as! MasterViewController
    controller.managedObjectContext = self.managedObjectContext
}


func application(application: UIApplication,
    openURL url: NSURL, options: [String: AnyObject]) -> Bool {
        NSLog("opened with url \(url)");
        FIRAuthUI.authUI()!.delegate = self;
        return FIRAuthUI.authUI()!.handleOpenURL(url, sourceApplication:options[UIApplicationOpenURLOptionsSourceApplicationKey] as! String);
}

Answer 1

I haven't tried this solution but this StackOverflow problem was linked to the FirebaseUI repo's issues section and someone there responded;

Obj-C: "There's a bug that prevents [[FIRAuthUI authUI] authViewController] from being used as the root view controller of your app. The workaround is to use a placeholder view controller as your app's root view controller, then present [[FIRAuthUI authUI] authViewController] on top of it."

for Swift users: There's a bug that prevents FIRAuthUI.authUI().authViewController() from being used as the root view controller of your app. The workaround is to use a placeholder view controller as your app's root view controller, then present FIRAuthUI.authUI().authViewController() on top of it.

Link: https://github.com/firebase/FirebaseUI-iOS/issues/65