I'm trying to use getX as flutter state management tool. GetX has its way handling language translation. One thing that I'm not sure is how could I initialise translation source from a remote server instead of hard code the translations. In such a way, I have the benefit of modifying translation without the need to release a new app.
Any suggest are welcome. Thanks.
I have DotNet WebAPI backend and I am sending translations like the following format:
[ApiController]
[Route("[controller]")]
public class TranslationsController : ControllerBase
{
[HttpGet]
public async Task<IActionResult> GetAll()
{
return Ok(new
{
en_US = new
{
hi = "Hi",
bye = "Bye"
},
bn_BD = new
{
hi = "ওহে",
bye = "বিদায়"
}
});
}
}
And my AppTranslations class:
class AppTranslations extends Translations {
final Map<String, String> en_US;
final Map<String, String> bn_BD;
AppTranslations({required this.en_US, required this.bn_BD});
static AppTranslations fromJson(dynamic json) {
return AppTranslations(
en_US: Map<String, String>.from(json["en_US"]),
bn_BD: Map<String, String>.from(json["bn_BD"]),
);
}
#override
Map<String, Map<String, String>> get keys => {
"en_US": en_US,
"bn_BD": bn_BD,
};
}
My TranslationProvider:
class TranslationProvider extends GetConnect {
Future<AppTranslations?> getTranslations() async {
final url = 'http://192.168.0.106:5000/translations';
final response = await get(url, decoder: AppTranslations.fromJson);
if (response.hasError) {
return Future.error(response.statusText!);
}
return response.body;
}
}
Then in my main function:
void main() async {
final translationProvider = TranslationProvider();
final translations = await translationProvider.getTranslations();
runApp(MyApp(translations: translations!));
}
And here's my MyApp:
class MyApp extends StatelessWidget {
final AppTranslations translations;
const MyApp({Key? key, required this.translations}) : super(key: key);
#override
Widget build(BuildContext context) {
return GetMaterialApp(
translations: translations,
locale: Locale("en_US"),
home: MyHomePage(),
);
}
}
And you are done! Now you can update your translations in the API and the update will reflect on the app.
So, after month worth of digging around, apparently Getx had its own method to add translations on the fly.
apiProvider.get('/api/translations').then((value) {
Get.clearTranslations();
Get.addTranslations(value.data['languages']);
}
virtually, you can call this anywhere you want!
Related
I am still a beginner with BLoC architecture. So far the UI updates when using int, bool, and other basic data types. But when it comes to Maps it really confuses me. My code basically looks like this:
my state
enum TalentStatus { initial, loading, loaded, error }
class TalentState extends Equatable {
const TalentState({
required this.talentStatus,
this.selectedService = const {},
required this.talents,
this.test = 0,
});
final TalentStatus talentStatus;
final Talents talents;
final Map<String, Service> selectedService;
final int test;
TalentState copyWith({
TalentStatus? talentStatus,
Talents? talents,
Map<String, Service>? selectedService,
int? test,
}) =>
TalentState(
selectedService: selectedService ?? this.selectedService,
talentStatus: talentStatus ?? this.talentStatus,
talents: talents ?? this.talents,
test: test ?? this.test,
);
#override
List<Object> get props => [talentStatus, talents, selectedService, test];
}
my event
abstract class TalentEvent extends Equatable {
const TalentEvent();
#override
List<Object> get props => [];
}
class TalentStarted extends TalentEvent {}
class TalentSelectService extends TalentEvent {
const TalentSelectService(
this.service,
this.talentName,
);
final Service service;
final String talentName;
}
and my bloc
class TalentBloc extends Bloc<TalentEvent, TalentState> {
TalentBloc(this._talentRepository)
: super(TalentState(
talentStatus: TalentStatus.initial, talents: Talents())) {
on<TalentSelectService>(_selectService);
}
final TalentRepository _talentRepository;
Future<void> _selectService(
TalentSelectService event,
Emitter<TalentState> emit,
) async {
state.selectedService[event.talentName] = event.service;
final selectedService = Map<String, Service>.of(state.selectedService);
emit(
state.copyWith(
selectedService: selectedService,
),
);
}
}
whenever an event TalentSelectService is called BlocBuilder doesn't trigger, what's wrong with my code?
Your Service object must be comparable. One suggestion is that it extends Equatable. Either way it have to implement (override) the == operator and hashCode
The reason your BlocBuilder doesn't trigger is (probably) that it doesn't recognize that there has been a change in the Map.
I'm fairly new to Flutter providers. I use Riverpod.
I have a Future provider that provide some data from a JSON file - in the future it will be from a API response.
import 'dart:convert';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../models/pokemon.dart';
final pokemonProvider = FutureProvider<List<Pokemon>>((ref) async {
var response =
await rootBundle.loadString('assets/mock_data/pokemons.json');
List<dynamic> data = jsonDecode(response);
return List<Pokemon>.from(data.map((i) => Pokemon.fromMap(i)));
});
I subscribe to with ref.watch in ConsumerState widgets, e.g.:
class PokemonsPage extends ConsumerStatefulWidget {
const PokemonsPage({Key? key}) : super(key: key);
#override
ConsumerState<PokemonsPage> createState() => _PokemonsPageState();
}
class _PokemonsPageState extends ConsumerState<PokemonsPage> {
#override
Widget build(BuildContext context) {
final AsyncValue<List<Pokemon>> pokemons =
ref.watch(pokemonProvider);
return pokemons.when(
loading: () => const CircularProgressIndicator(),
error: (err, stack) => Text('Error: $err'),
data: (pokemons) {
return Material(
child: ListView.builder(
itemCount: pokemons.length,
itemBuilder: (context, index) {
Pokemon pokemon = pokemons[index];
return ListTile(
title: Text(pokemon.name),
);
},
));
},
);
}
}
But in that case, what is the best practice to write/update data to the JSON file/API?
It seems providers are used for reading/providing data, not updating it, so I'm confused.
Should the same provider pokemonProvider be used for that? If yes, what is the FutureProvider method that should be used and how to call it? If not, what is the best practice?
I am new to riverpod too but I'll try to explain the approach we took.
The examples with FutureProviders calling to apis are a little bit misleading for me, because the provider only offers the content for a single api call, not access to the entire api.
To solve that, we found the Repository Pattern to be very useful. We use the provider to export a class containing the complete api (or a mock one for test purposes), and we control the state (a different object containing the different situations) to manage the responses and updates.
Your example would be something like this:
First we define our state object:
enum PokemonListStatus { none, error, loaded }
class PokemonListState {
final String? error;
final List<Pokemon> pokemons;
final PokemonListStatus status;
const PokemonListState.loaded(this.pokemons)
: error = null,
status = PokemonListStatus.loaded,
super();
const PokemonListState.error(this.error)
: pokemons = const [],
status = PokemonListStatus.error,
super();
const PokemonListState.initial()
: pokemons = const [],
error = null,
status = PokemonListStatus.none,
super();
}
Now our provider and repository class (abstract is optional, but let's take that approach so you can keep the example for testing):
final pokemonRepositoryProvider =
StateNotifierProvider<PokemonRepository, PokemonListState>((ref) {
final pokemonRepository = JsonPokemonRepository(); // Or ApiRepository
pokemonRepository.getAllPokemon();
return pokemonRepository;
});
///
/// Define abstract class. Useful for testing
///
abstract class PokemonRepository extends StateNotifier<PokemonListState> {
PokemonRepository()
: super(const PokemonListState.initial());
Future<void> getAllPokemon();
Future<void> addPokemon(Pokemon pk);
}
And the implementation for each repository:
///
/// Class to manage pokemon api
///
class ApiPokemonRepository extends PokemonRepository {
ApiPokemonRepository() : super();
Future<void> getAllPokemon() async {
try {
// ... calls to API for retrieving pokemon
// updates cached list with recently obtained data and call watchers.
state = PokemonListState.loaded( ... );
} catch (e) {
state = PokemonListState.error(e.toString());
}
}
Future<void> addPokemon(Pokemon pk) async {
try {
// ... calls to API for adding pokemon
// updates cached list and calls providers watching.
state = PokemonListState.loaded([...state.pokemons, pk]);
} catch (e) {
state = PokemonListState.error(e.toString());
}
}
}
and
///
/// Class to manage pokemon local json
///
class JsonPokemonRepository extends PokemonRepository {
JsonPokemonRepository() : super();
Future<void> getAllPokemon() async {
var response =
await rootBundle.loadString('assets/mock_data/pokemons.json');
List<dynamic> data = jsonDecode(response);
// updates cached list with recently obtained data and call watchers.
final pokemons = List<Pokemon>.from(data.map((i) => Pokemon.fromMap(i)));
state = PokemonListState.loaded(pokemons);
}
Future<void> addPokemon(Pokemon pk) async {
// ... and write json to disk for example
// updates cached list and calls providers watching.
state = PokemonListState.loaded([...state.pokemons, pk]);
}
}
Then in build, your widget with a few changes:
class PokemonsPage extends ConsumerStatefulWidget {
const PokemonsPage({Key? key}) : super(key: key);
#override
ConsumerState<PokemonsPage> createState() => _PokemonsPageState();
}
class _PokemonsPageState extends ConsumerState<PokemonsPage> {
#override
Widget build(BuildContext context) {
final statePokemons =
ref.watch(pokemonRepositoryProvider);
if (statePokemons.status == PokemonListStatus.error) {
return Text('Error: ${statePokemons.error}');
} else if (statePokemons.status == PokemonListStatus.none) {
return const CircularProgressIndicator();
} else {
final pokemons = statePokemons.pokemons;
return Material(
child: ListView.builder(
itemCount: pokemons.length,
itemBuilder: (context, index) {
Pokemon pokemon = pokemons[index];
return ListTile(
title: Text(pokemon.name),
);
},
));
}
}
}
Not sure if this is the best approach but it is working for us so far.
you can try it like this:
class Pokemon {
Pokemon(this.name);
final String name;
}
final pokemonProvider =
StateNotifierProvider<PokemonRepository, AsyncValue<List<Pokemon>>>(
(ref) => PokemonRepository(ref.read));
class PokemonRepository extends StateNotifier<AsyncValue<List<Pokemon>>> {
PokemonRepository(this._reader) : super(const AsyncValue.loading()) {
_init();
}
final Reader _reader;
Future<void> _init() async {
final List<Pokemon> pokemons;
try {
pokemons = await getApiPokemons();
} catch (e, s) {
state = AsyncValue.error(e, stackTrace: s);
return;
}
state = AsyncValue.data(pokemons);
}
Future<void> getAllPokemon() async {
state = const AsyncValue.loading();
/// do something...
state = AsyncValue.data(pokemons);
}
Future<void> addPokemon(Pokemon pk) async {}
Future<void> updatePokemon(Pokemon pk) async {}
Future<void> deletePokemon(Pokemon pk) async {}
}
So I wanted to use Hive for storing notes in a Calendar app but I am stuggling so much with implementing Hive and a ChangeNotifierProvider together . If anyone has an idea on what to do I would like to see it.
Here is my code until now :
#HiveType(typeId: 0)
class EventsBox extends HiveObject {
EventsBox({required this.date, required this.eventsList});
#HiveField(0)
DateTime date;
#HiveField(1)
List<CleanCalendarEvent> eventsList;
}
And here is the FutureProvider that is needed :
final hiveProvider = FutureProvider<HiveDB>((_) => HiveDB.create());
class HiveDB {
var _events;
HiveDB._create() {}
static Future<HiveDB> create() async {
final component = HiveDB._create();
await component._init();
return component;
}
_init() async {
Hive.registerAdapter(EventsBoxAdapter());
this._events = await Hive.openBox<EventsBox>('events');
}
storeEvent(EventsBox eventsMap) {
this._events.put('events', eventsMap);
}
EventsBox getEvents() {
return this._events.get('events');
}
}
I want to use ChangeNotifierProvider and not FutureProvider
The goal of the provider framework is to inject dependencies into your app without recreating them all the time. In your example, you have your HiveDB class which is what you want to inject into your app for various other widgets to use it.
IMO, the general approach of "providing" dependencies is:
Create dependency instances outside the app (Typically in the main() function)
Create a provider which injects this dependency object
Wrap your MaterialApp with the provider
Supply your dependency object into the provider wrapper
Use the Provider<DependencyClass>.of(context) to access your dependency wherever you need it in your app.
Let's see how this applies to your code:
1. Setup your Hive models and HiveDB
lib/models/event_box.dart
#HiveType(typeId: 0)
class EventsBox extends HiveObject {
#HiveField(0)
DateTime date;
#HiveField(1)
List<CleanCalendarEvent> eventsList;
EventsBox({
required this.date,
required this.eventsList,
});
}
lib/models/hive_db.dart
class HiveDB {
var _events;
HiveDB._create() {}
static Future<HiveDB> create() async {
final component = HiveDB._create();
await component._init();
return component;
}
_init() async {
Hive.registerAdapter(EventsBoxAdapter());
this._events = await Hive.openBox<EventsBox>('events');
}
storeEvent(EventsBox eventsMap) {
this._events.put('events', eventsMap);
}
EventsBox getEvents() {
return this._events.get('events');
}
}
In this case, you want to "provide" (or inject) an instance of HiveDB to your app.
2. Create a provider for your HiveDB instance
lib/models/hive_db_provider.dart
class HiveDbProvider extends StatelessWidget {
final HiveDB db;
final Widget child;
const HiveDbProvider({
Key? key,
required this.db,
required this.child,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return ChangeNotifierProvider<HiveDB>.value(
value: db,
child: Consumer<AppCache>(
builder: (context, db, _) {
return child;
},
),
);
}
}
3. Create HiveDB instance in main()
lib/main.dart
void main() async {
final HiveDB db = await HiveDB.create();
runApp(
MyApp(db: db)
);
}
...
4. Inject the HiveDB instance using the provider
lib/main.dart
...
class MyApp extends StatelessWidget {
final HiveDB db;
const PayBuddy({
Key? key,
required this.db,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return HiveDbProvider(
db: db,
child: CacheProvider(
cache: cache,
child: MaterialApp(
...
),
),
);
}
}
5. Access "provided" instance using Provider anywhere in your app
lib/pages/some_screen.dart
import "package:provider/provider.dart";
...
class SomeScreen extends StatelessWidget {
#override
Widget build(BuildContext context) {
// Access HiveDB instance
final hiveDb = Provider<HiveDB>.of(context);
...
}
}
Conclusion
The sample uses the Provider package which simplifies using provider usage in Flutter.
I am trying to fix an issue related to Flutter Bloc. I am editing someone else code to make it work with the latest flutter_bloc version but I am unable to do so. Can someone do a rewrite for my code so I can run it? I saw many answers but I am unable to understand how to fix my own code.
This is the complete code for all_categories_bloc.dart
class AllCategoriesBloc extends Bloc<AllCategoriesEvent, AllCategoriesState> {
AllCategoriesBloc({
this.apiRepository,
}) : super(AllCategoriesInitial()) {
on<GetAllCategories>(_onGetAllCategories);
}
final ApiRepository apiRepository;
Future<void> _onGetAllCategories(
GetAllCategories event,
Emitter<AllCategoriesState> emit,
) async {
try {
emit(const AllCategoriesLoading());
final categoriesModel = await apiRepository.fetchCategoriesList();
emit(AllCategoriesLoaded(categoriesModel));
if (categoriesModel.error != null) {
emit(AllCategoriesError(categoriesModel.error));
}
} catch (e) {
emit(
const AllCategoriesError(
"Failed to fetch all categories data. Is your device online ?",
),
);
}
}
}
Code for all_categories_event.dart
abstract class AllCategoriesEvent extends Equatable {
AllCategoriesEvent();
}
class GetAllCategories extends AllCategoriesEvent {
#override
List<Object> get props => null;
}
Code for all_categories_state.dart
abstract class AllCategoriesState extends Equatable {
const AllCategoriesState();
}
class AllCategoriesInitial extends AllCategoriesState {
AllCategoriesInitial();
#override
List<Object> get props => [];
}
class AllCategoriesLoading extends AllCategoriesState {
const AllCategoriesLoading();
#override
List<Object> get props => null;
}
class AllCategoriesLoaded extends AllCategoriesState {
final CategoriesModel categoriesModel;
const AllCategoriesLoaded(this.categoriesModel);
#override
List<Object> get props => [categoriesModel];
}
class AllCategoriesError extends AllCategoriesState {
final String message;
const AllCategoriesError(this.message);
#override
List<Object> get props => [message];
}
It throws an error "Bad state: add(GetAllCategories) was called without a registered event handler.
Make sure to register a handler via on((event, emit) {...})"
I have this add(GetAllCategories) in my home. dart file but the solution is to edit this code which I am unable to do so. Can someone do a rewrite for the latest bloc? I would be thankful.
Let's get through the migration guide step by step:
package:bloc v5.0.0: initialState has been removed. For more information check out #1304.
You should simply remove the AllCategoriesState get initialState => AllCategoriesInitial(); portion from your BLoC.
package:bloc v7.2.0 Introduce new on<Event> API. For more information, read the full proposal.
As a part of this migration, the mapEventToState method was removed, each event is registered in the constructor separately with the on<Event> API.
First of all, register your events in the constructor:
AllCategoriesBloc() : super(AllCategoriesInitial()) {
on<GetAllCategories>(_onGetAllCategories);
}
Then, create the _onGetAllCategories method:
Future<void> _onGetAllCategories(
GetAllCategories event,
Emitter<AllCategoriesState> emit,
) async {
try {
emit(const AllCategoriesLoading());
final categoriesModel = await _apiRepository.fetchCategoriesList();
emit(AllCategoriesLoaded(categoriesModel));
if (categoriesModel.error != null) {
emit(AllCategoriesError(categoriesModel.error));
}
} catch (e) {
emit(
const AllCategoriesError(
"Failed to fetch all categories data. Is your device online ?",
),
);
}
}
Notice, that instead of using generators and yielding the next state, you should use the Emitter<AllCategoriesState> emitter.
Here is the final result of the migrated AllCategoriesBloc:
class AllCategoriesBloc extends Bloc<AllCategoriesEvent, AllCategoriesState> {
AllCategoriesBloc() : super(AllCategoriesInitial()) {
on<GetAllCategories>(_onGetAllCategories);
}
final ApiRepository _apiRepository = ApiRepository();
Future<void> _onGetAllCategories(
GetAllCategories event,
Emitter<AllCategoriesState> emit,
) async {
try {
emit(const AllCategoriesLoading());
final categoriesModel = await _apiRepository.fetchCategoriesList();
emit(AllCategoriesLoaded(categoriesModel));
if (categoriesModel.error != null) {
emit(AllCategoriesError(categoriesModel.error));
}
} catch (e) {
emit(
const AllCategoriesError(
"Failed to fetch all categories data. Is your device online ?",
),
);
}
}
}
Bonus tip
Instead of creating an instance of ApiRepository inside the BLoC directly, you can use the constructor injection:
class AllCategoriesBloc extends Bloc<AllCategoriesEvent, AllCategoriesState> {
AllCategoriesBloc({
required this.apiRepository,
}) : super(AllCategoriesInitial()) {
on<GetAllCategories>(_onGetAllCategories);
}
final ApiRepository apiRepository;
...
}
Now, when creating BLoC, pass the instance of the repository to the constructor, like AllCategoriesBloc(apiRepository: ApiRepository()). This way you will be able to properly unit test your BLoC by mocking dependencies (in this case, ApiRepository).
I'm trying to figure out the BLoC library, but it gives me headaches.
I'm trying to fetch hotel names from an API. I have a model and a service responsible for contacting the API and fetching the data. However, I don't know how to connect it to the BLoC library.
Once my app starts, I want BLoC to fetch the data from the API and then show it in the app.
Here's my code:
hotel_model.dart
class Hotels {
final List<Hotel> hotels;
Hotels({this.hotels});
factory Hotels.fromJson(Map<String, dynamic> json) {
return Hotels(
hotels: List<Hotel>.from(
json['hotels'].map(
(x) => Hotel.fromJson(x),
),
),
);
}
}
class Hotel {
final String hotelName;
Hotel({this.hotelName});
factory Hotel.fromJson(Map<String, dynamic> json) {
return Hotel(
hotelName: json['name'],
);
}
}
hotel_service.dart
import 'package:http/http.dart' as http;
abstract class DownloadService {
Future<http.Response> fetchHotels();
}
class HotelService extends DownloadService {
#override
Future<http.Response> fetchHotels() {
final Uri uri = Uri.https('services.lastminute.com', 'mobile/stubs/hotels');
return http.get(uri);
}
}
And here's what I did wit the BLoC lib.
hotel_event.dart
part of 'hotel_bloc.dart';
#immutable
abstract class HotelEvent {}
class OnAppStartEvent extends HotelEvent {}
hotel_bloc.dart
import 'dart:async';
import 'package:bloc/bloc.dart';
import 'package:hotels/models/hotel/hotel_model.dart';
import 'package:hotels/services/hotel/hotel_service.dart';
import 'package:meta/meta.dart';
part 'hotel_event.dart';
part 'hotel_state.dart';
class HotelBloc extends Bloc<HotelEvent, HotelState> {
HotelBloc() : super(HotelFinal());
final HotelService hotelService = HotelService();
#override
Stream<HotelState> mapEventToState(
HotelEvent event,
) async* {
if (event is FetchEvent) {
final response = hotelService.fetchHotels();
yield
}
}
}
hotel_state.dart
part of 'hotel_bloc.dart';
#immutable
abstract class HotelState {
HotelState();
}
class HotelFinal extends HotelState {
final Hotel hotel;
HotelFinal(this.hotel);
Hotel getHotel() {
return hotel;
}
}
First of all add await to this line in your bloc
final response = await hotelService.fetchHotels();
return List<Hotel> from your fetchHotels function
you must have stateful class for your screen and in the initState
you can create your bloc object and call .add method on it
in your build method wrap your widget with BlocBuilder and on builder callback check your bloc state, if the state is HotelFinal return your ui with list of hotels in your state object.
It'll be useful to add another state for your HotelState for when your bloc is fetching the data, and even for when there's an error. e.g;
part of 'hotel_bloc.dart';
#immutable
abstract class HotelState {
HotelState();
}
class HotelFinal extends HotelState {
final Hotel hotel;
HotelFinal(this.hotel);
Hotel getHotel() {
return hotel;
}
}
class HotelLoading extends HotelState {
HotelLoading();
}
class HotelError extends HotelState {
final String error;
HotelError(this.error);
}
You would want to change your mapEventToState to something like this:
#override
Stream<HotelState> mapEventToState(
HotelEvent event,
) async* {
if (event is FetchEvent) {
yield HotelLoading();
try {
final response = await hotelService.fetchHotels();
// It seems like your service doesn't return an hotel directly, so you'll have to deal with this as it is not part of the question.
final hotel = getYourHotelHereWithTheResponse;
yield HotelFinal(hotel);
} catch (e) {
yield HotelError('something went wrong getting the hotel info');
}
}
}
Lastly, add a widget to your widget tree that adds FetchEvent to your bloc and add a BlocBuilder to react to the change of states. Note that this is very flexible and can be done in many ways, but it is out of the scope of your very broad question, I'm just showing you how to use the library at a minimal:
class MyStatefulWidget extends StatefulWidget {
#override
_MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
HotelBloc hotelBloc;
#override
void initState() {
hotelBloc = HotelBloc..add(FetchEvent());
super.initState();
}
#override
void dispose() {
hotelBloc.close();
super.dispose();
}
#override
Widget build(BuildContext context) {
return BlocBuilder(builder: (context, state) {
if(state is HotelLoading) {
// return a widget to deal with loading
}
if(state is HotelFinal) {
// return a widget to deal with success
}
if(state is HotelError) {
// return a widget to deal with error
}
});
}
}