I have setup a riverpod provider in order to listen to a document in firestore as shown below.
My assumption was that the document is only read once after the start of the app and then only read / charged when the content has changed.
When I run the firestore emulator it shows me frequent GET calls against this object.
Is there a way to stream a single object without document reads or do I have to use a query snapshot for that?
final habitProvider =
StateNotifierProvider<ObjectRepository, AsyncValue<Object>>(
(ref) => ObjectRepository(ref.read));
class ObjectRepository extends StateNotifier<AsyncValue<Object>> {
final Reader _reader;
StreamSubscription<Object>? _subscription;
ObjectRepository(this._reader) : super(AsyncData(Object.empty())) {
state = const AsyncLoading();
try {
_subscription?.cancel();
_subscription = getObject().listen((event) {
state = AsyncData(event);
});
} catch (e) {
state = AsyncError(e);
}
}
Stream<HabitCollection> getObject() {
final docReference =
_reader(firebaseFirestoreProvider).collection("x").doc("y");
final snapshot = docReference.snapshots();
return snapshot.map((snapshot) {
if (snapshot.data() == null) {
return Object.empty();
} else {
return Object.fromJson(
snapshot.data() as Map<String, dynamic>);
}
});
}
void dispose() {
_subscription?.cancel();
super.dispose();
}
}
Related
I have a problem, my database has data, but I can't list this data in the application, can you see where the problem is?
Here the database query is being implemented
#override
Stream<Either<TodoFailures, List<Todo>>> watchAll() async* {
//yield left(const InsufficientPermissions());
// users/{user ID}/notes/{todo ID}
final userDoc = await firestore.userDocument();
yield* userDoc.todoCollection
.snapshots()
.map((snapshot) => right<TodoFailures, List<Todo>>(snapshot.docs
.map((doc) => TodoModel.fromFirestore(doc).toDomain()).toList()))
.handleError((e) {
if (e is FirebaseException) {
if (e.code.contains('permission-denied') || e.code.contains("PERMISSION_DENIED")) {
return left(InsufficientPermisssons());
} else {
return left(UnexpectedFailure());
}
} else {
// ? check for the unauthenticated error
// ! log.e(e.toString()); // we can log unexpected exceptions
return left(UnexpectedFailure());
}
});
}
Below is where I capture the integrated query through the BloC
#injectable
class ObserverBloc extends Bloc<ObserverEvent, ObserverState> {
final TodoRepository todoRepository;
StreamSubscription<Either<TodoFailures, List<Todo>>>? todoStreamSubscription;
ObserverBloc({required this.todoRepository}) : super(ObserverInitial()) {
on<ObserverEvent>((event, emit) async {
emit(ObserverLoading());
await todoStreamSubscription?.cancel();
todoStreamSubscription = todoRepository
.watchAll()
.listen((failureOrTodos) => add(TodosUpdatedEvent(failureOrTodos: failureOrTodos)));
});
on<TodosUpdatedEvent>((event, emit) {
event.failureOrTodos.fold((failures) => emit(ObserverFailure(todoFailure: failures)),
(todos) => emit(ObserverSuccess(todos: todos)));
});
}
#override
Future<void> close() async {
await todoStreamSubscription?.cancel();
return super.close();
}
}
Even containing data in the database it comes empty, I need help to know where the problem is.
I created a local database using flutter sqflite. And I want to listen to a length of a list of tasks on that database and update the total count of the tasks, when I add something or remove from that list. But when I call provider.of(context) thing, it doesn't update themselves, means it doesn't listen. I used a stream to grab the database data and show in the UI.
Here is the database class I created:
class TaskDatabase with ChangeNotifier {
final String dbName = 'db.sqlite';
Database? _db;
List<Task> _tasksList = [];
int _totalTaskCount = 0;
final _streamController = StreamController<List<Task>>.broadcast();
Stream<List<Task>> all() =>
_streamController.stream.map((tasks) => tasks..sort());
int get totalTasksCount {
return _totalTaskCount;
}
Future<bool> close() async {
final db = _db;
if (db == null) {
return false;
}
await db.close();
return true;
}
Future<bool> open() async {
if (_db != null) {
return true;
}
final directory = await getApplicationDocumentsDirectory();
final path = '${directory.path}/$dbName';
try {
final db = await openDatabase(path);
_db = db;
//creating the database table using sqflite
const createTable = '''CREATE TABLE IF NOT EXISTS "TABLEOFTASKS" (
"id" INTEGER NOT NULL,
"taskTitle" TEXT,
"isDone" INTEGER NOT NULL DEFAULT 0,
PRIMARY KEY("id" AUTOINCREMENT));''';
await db.execute(createTable);
// read all existing task objects from the db
_tasksList = await _fetchTasks();
_streamController.add(_tasksList);
return true;
} catch (e) {
// print('error = $e');
return false;
}
}
// Creating a new task and save to the database:
// other CRUD functions are not added here:)
Future<bool> create(String taskTitle) async {
final db = _db;
if (db == null) {
return false;
}
try {
final id = await db.insert(
'TABLEOFTASKS',
{
'taskTitle': taskTitle,
'isDone': 0,
},
);
final task = Task(
id: id,
taskTitle: taskTitle,
isDone: false,
);
_tasksList.add(task);
_streamController.add(_tasksList);
_totalTaskCount = _tasksList.length;
notifyListeners();
return true;
} catch (e) {
print('error in creating task = $e');
return false;
}
}
}
Here is the widget that I want to listen and update:
final int taskCount = Provider.of<TaskDatabase>(context, listen: true).totalTasksCount;
.
.
.
Text(taskCount.toString()),
I added the provider at the top of the widget tree and there are no errors. Only thing happening is not updating the text widget
I created a streamBuilder and grabbed the list I want as a snapshot. Updating the list length using the provider package did not work. You can find in the DB class in the question to find how I created a stream of Tasks. Firest initialize the Database in init method.
late final TaskDatabase _crudStorage;
#override
void initState() {
_crudStorage = TaskDatabase();
_crudStorage.open();
super.initState();
}
#override
void dispose() {
_crudStorage.close();
super.dispose();
}
....
return Scaffold(
resizeToAvoidBottomInset: false,
drawer: const CustomDrawer(),
body: StreamBuilder(
stream: _crudStorage.all(),
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.active:
case ConnectionState.waiting:
if (snapshot.data == null) {
return const Center(child: Shimmer());
}
final tasksList = snapshot.data as List<Task>; /// The List I want
.
.
.
.
.
.
SomeTextWidget('The length of tasks = ${tasksList.length}'),
final loginProvider =
FutureProvider.family<bool, LoginParam>((ref, param) async {
if (param.sgId == '' || param.password == '') {
return false;
}
final http.Response response =
await APIClient().login(param.sgId, param.password);
if (response.statusCode == 200) {
await APIClient().saveTokens(response);
UserDefaultEntity entity =
await ref.watch(userDefaultsProvider(param.sgId).future);
//ref.state = AsyncValue.data(true);
return true;
} else {
throw Exception(jsonDecode(response.body)['message'] ?? 'Unknown Error');
}
});
void login(String userName, String password) async {
state = AsyncValue.loading();
AsyncValue<bool> result;
try {
result = await ref.refresh(loginProvider(LoginParam(userName, password)));
state = result;
} catch (e) {
state = AsyncError(e);
}
}
I'm trying to throw an custom exception inside riverpod future provider and catch the exception in other state notifier classes, but the catch block is not triggered.
Is there any other way to handle exceptions that future provider throw.
First of all, you won't have to manually catch errors inside a FutureProvider, it will do that for you. Refer this example.
Generally, the operations that happen after certain "user interaction" like a button click (in this case, login operation), are not meant to be written in FutureProvider. Scenarios where you'd be using FutureProvider are as follows:
Fetching some data over HTTP/HTTPS.
Performing operations like reading a file or a local database.
So your use case of login can be achieved using a StateNotifier.
// auth_provider.dart
import 'package:hooks_riverpod/hooks_riverpod.dart';
// Always prefer some strongly typed object to
// know current status of authentication.
enum AuthState {
unauthenticated,
authenticated,
authenticating,
failed,
}
// StateNotifier is recommended to encapsulate all your business
// logic into a single class and use it from there.
class AuthStateNotifier extends StateNotifier<AuthState> {
// Initialize with the default state of "unauthenticated".
const AuthStateNotifier() : super(AuthState.unauthenticated);
Future<void> login(LoginParam params) async {
if (param.sgId.isEmpty || param.password.isEmpty) {
state = AuthState.failed;
return;
}
final http.Response response = await APIClient().login(param.sgId, param.password);
if (response.statusCode == 200) {
await APIClient().saveTokens(response);
UserDefaultEntity entity = await ref.watch(userDefaultsProvider(param.sgId).future);
state = AuthState.authenticated;
return;
} else {
state = AuthState.failed;
throw Exception(jsonDecode(response.body)['message'] ?? 'Unknown Error');
}
}
}
// Finally, create a provider that can be consumed in the presentation layer (UI).
final authProvider = StateNotifierProvider<AuthStateNotifier, AuthState>((ref) => const AuthStateNotifier());
Then, in your UI part, usually in the onTap / onPressed event handler of button, you can use it as follows. Please note that, we have created a button widget that extends the ConsumerWidget to access the ref.
// login.dart
import 'auth_provider.dart';
class LoginButton extends ConsumerWidget {
final LoginParam params;
const LoginButton({
Key? key,
required this.params,
}) : super(key: key);
#override
Widget build(BuildContext context, WidgetRef ref) {
void login() {
try {
await ref.read(authProvider.notifier).login(params);
} catch (e) {
// Handle error here.
}
}
return ElevatedButton(
child: Text('Login'),
// Call the handler here.
onPressed: login,
);
}
}
Hello i am trying to get data from firestore map it to a stream i am using Rxdart how do i add this Stream of list of product to the stream.When i tried to do it it keeps saying.The argument type Stream> can't be assigned to parameter type List.I am new to flutter please help.
Product Service;
class ProductService {
Firestore _db = Firestore.instance;
var random = Random();
Stream<List<Product>> fetchProducts() {
return _db.collection('products').snapshots().map(
(snapshot) => snapshot.documents
.map((document) => Product.fromFirestore(document.data))
.toList(),
);
}
}
bloc
class ProductBloc {
final _products = BehaviorSubject<List<Product>>();
final ProductService _db = ProductService();
//getters
Stream<List<Product>> get products => _products.stream;
Function(List<Product>) get changeProducts => _products.sink.add;
loadData() async {
try {
var products = _db.fetchProducts();
_products.sink.add(products);
} catch (err) {
print(err);
}
}
dispose() {
_products.close();
}
}
I am developing a simple chat application, and I had to check-end API with specific time intervals.
but in my BLOC logic I used Observable
So how can I change codes to make this stream periodic?
final bloc = ConversationBloc();
class ConversationBloc {
final repository = Repository();
final conversationFetcher = PublishSubject<ConversationModel>();
final conversationFetcherStatus = PublishSubject<MessageModel>();
Observable<ConversationModel> get userConversation =>
conversationFetcher.stream;
dispose() async {
await conversationFetcher.drain();
conversationFetcher.close();
conversationFetcherStatus.close();
}
fetchUserConversation(toUsernameController) async {
ConversationModel conversationModel =
await repository.fetchUserConversation(toUsernameController);
conversationFetcher.sink.add(conversationModel);
}
saveConversation(Data conversation) async {
try {
MessageModel conversationModel =
await repository.saveConversation(conversation);
conversationFetcherStatus.sink.add(conversationModel);
} catch (e) {
conversationFetcherStatus.sink.addError(e);
}
}
fetchUserConversationList(int toUsernameController) async {
ConversationModel conversationModel =
await repository.fetchUserConversationList(toUsernameController);
conversationFetcher.sink.add(conversationModel);
}
}