Authenticate game Center

Code Block 
func authenticatePlayer() {
        GKLocalPlayer.local.authenticateHandler = { gcAuthVC, error in
           
        // In your delegate, implement method `didChangeAuthStatus`, for example to enable a Game Center button
        self.delegate?.didChangeAuthStatus(isAuthenticated: GKLocalPlayer.local.isAuthenticated)
        // This is called if the local player gets authenticated. Nothing happens, GKLocalPlayer gets registered
        if GKLocalPlayer.local.isAuthenticated {
                GKLocalPlayer.local.register(self)
        }
         // This is called, when a player opens your app and he|she is not authenticated. 
         // It opens a viewController with sign-in info
        else if let vc = gcAuthVC {
                self.delegate?.presentGameCenterAuth(viewController: vc)
        }
        // Handing an error while authenticating
        else {
                print(">>>>> Error authenticating the Player! \(error?.localizedDescription ?? "none") <<<<<")
        }
}

Code Block 
override func didMove(to view: SKView) {
     GameCenterHelper.sharedInstance.delegate = self
     GameCenterManager.sharedInstance.authenticatePlayer()
 }
@objc func didChangeAuthStatus(isAuthenticated: Bool) {
       ... For example, stop spinning activity indicator
       if indicator != nil {
            indicator!.stop()
            indicator!.removeFromSuperview()
            indicator = nil
        }
        ... Or enable the *PLAY ON GAMECENTER* button
        if GKLocalPlayer.local.isAuthenticated {
            btnPlayGameCenter.setButtonLabel(title: btnPlayGameCenterTitle(), font: "Noteworthy-Bold", fontSize: 40)
}
    
    /** Present the view controller with the Sign-in info */
    func presentGameCenterAuth(viewController: UIViewController?) {
        guard let vc = viewController else {return}
        self.view!.window?.rootViewController?.present(vc, animated: true)
 }