The document discusses different state management approaches in Flutter including Provider, BLoC, and Redux. It provides code examples for implementing user authentication and login using the Provider and BLoC patterns. Additional resources are referenced at the end for learning more about Redux principles and the Provider package in Flutter.

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@override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider(builder: (context) =>
UserLogin()),
//hint: other providers go here
],
child: Scaffold(
appBar: AppBar( …. )
)
);
}
class UserLogin with ChangeNotifier {
String _user;
….
}
UserLogin userLogin = Provider.of<UserLogin>(context);
userLogin.someAction();
userLogin.notifyListeners(); // usually inside another method

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class UserSignInBloc {
Sink<UserLogin> get login => _userCredentialsStream.sink;
final _userCredentialsStream = BehaviorSubject<UserLogin>();
Stream<UserAuthenticationState> userSigned;
UserSignInBloc() {
userSigned = Observable.merge([
_userCredentialsStream.stream.switchMap(_signIn),
// other login methods go here
]).asBroadcastStream();
}
void dispose() {
_userCredentialsStream.close();
}
// Business logic here
}
_userSignInBloc.login.add(UserLogin(user, password));

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var _userSignInBloc = UserSignInBloc();
ResultWidget(_userSignInBloc.userSigned),
class ResultWidget extends StatefulWidget {
Stream<UserAuthenticationState> userSigned;
ResultWidget(this.userSigned);
@override
_ResultWidgetState createState() => _ResultWidgetState(userSigned);
}
class _ResultWidgetState extends State<ResultWidget> {
var loginResultText = "";
_ResultWidgetState(Stream<UserAuthenticationState> userSigned){
userSigned.listen(onLoginDataChanged);
}
void onLoginDataChanged(UserAuthenticationState event) {
if (event is UserAuthenticationLoading) {
setState(() {
loginResultText = "LOADING...";
});
}
}

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final store = Store<AppState>(
appReducer,
initialState: AppState.noLoggedUser(),
middleware: createStoreLoginMiddleware(),
);
@override
Widget build(BuildContext context) {
return StoreProvider(
store: store,
child: MaterialApp( … )
);
}
UserLogin user = StoreProvider.of<AppState>(context).state.loggedUser;
StoreProvider.of<AppState>(context).dispatch(LoginRequestAction(user,
password));
class LoginUnsuccessfulAction {}
TypedReducer<UserLogin, LoginSuccessfulAction>(_setUser)
UserLogin _setUser(UserLogin user, LoginSuccessfulAction action) {
print("Previous user: $user , storing new user: ${action.user}");
return action.user;
}

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https://github.com/kosiara/bloc-vs-pprov-vs-redux

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Bartosz Kosarzycki
Poznań Flutter Developer Group
facebook.com/poznanflutter
meetup.com/poznan-flutter-developers

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https://redux.js.org/introduction/three-principles
https://www.youtube.com/watch?v=Zbm3hjPjQMk
https://www.udemy.com/course/react-redux/
https://medium.com/flutter-community/flutter-pragmatic-state-
management-using-provider-5c1129f9b5bb
https://pub.dev/packages/provider