class MyViewController: UIViewController, GPPSignInDelegate {

@IBAction func enterGooglePlusButton(sender: AnyObject) {
var signin = GPPSignIn.sharedInstance()
signin.shouldFetchGooglePlusUser = true
signin.clientID = googlePlusClientID // This is the client id
signin.scopes = [kGTLAuthScopePlusLogin]
signin.delegate = self
signin.authenticate()
}

func finishedWithAuth(auth: GTMOAuth2Authentication!, error: NSError!) {
    if error == nil {
        Logger.write(auth)
    } else {
        Logger.write(error)
    }
}