import 'package:flutter/material.dart'; abstract class LoginCredentials extends ChangeNotifier { String get fullname; bool get isLoggedIn; void setLoggedIn(bool loggedIn); void logout(); } class LoginCredentialsImpl extends LoginCredentials { bool loggedIn = false; @override bool get isLoggedIn => loggedIn; @override String get fullname => ""; @override void setLoggedIn(bool loggedIn) { this.loggedIn = loggedIn; } @override void logout() { loggedIn = false; notifyListeners(); } }