您可以使用UserDefault进行检查.只需维护该标志即可检查

You can use UserDefault to check the same. Just maintain the flag to check

喜欢

    GIDSignIn.sharedInstance().signInSilently()


   Auth.auth().addStateDidChangeListener { (auth, user) in
        if user != nil {
             if UserDefaults.standard.string(forKey: "uid") != nil && Auth.auth().currentUser != nil {
              //User was already logged in 
               }

             UserDefaults.standard.setValue(user?.uid, forKeyPath: "uid")

            self.performSegue(withIdentifier: "CurrentlyLoggedIn", sender: nil)

        }
    }