While this yield in setData method doesnot work can anyone describe this?? If no parameter is sent from setData then it works. Or anyone can explain yeild how it works in bloc.
class LoginerrorBloc extends Bloc<LoginerrorEvent, LoginerrorState> {
#override
LoginerrorState get initialState => InitialLoginerrorState();
#override
Stream<LoginerrorState> mapEventToState(
LoginerrorEvent event,
) async* {
if (event is LoginEvent) {
yield LoginLoading();
try {
final url = apiUrl + 'login';
http.Response response = await http.post(url,
body: {'contact': event.contact, 'password': event.password});
if (response.statusCode == 200) {
// var res = Authenticate.fromJson(true);
yield* setData(Login.fromJson(jsonDecode(response.body)));
} else if (response.statusCode == 401) {
var res = LoginError.fromJson(jsonDecode(response.body));
yield LoginErrorState(res);
} else {
var res = LoginError.fromJson({'message': 'Internal Server Error'});
yield LoginErrorState(res);
}
} catch (e) {
var res = NetworkError.fromJson({'message': 'Internal Server Error'});
yield NetworkErrorState(res);
}
}
}
Stream<LoginerrorState> setData(data) async* {
yield AuthenticateState();
}
}
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 have a simple flutter code to retrieve some data from Firestore. the data is retireved correctly, however passing the data from the future function making the result always null. can you advise how to adapt the code to return the list?
that is the class where the actual query is happening:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
List businessprofileslist = [];
try {
await BusinessProfilesCollection.get().then((QuerySnapshot) {
QuerySnapshot.docs.forEach((element) {
businessprofileslist.add(element.data());
print(businessprofileslist[0]);
});
});
} catch (e) {
print(e.toString());
return null;
}
}
}
here is the page where I am calling the function: (however the result is always null)
class _ProfilesListPageState extends State<ProfilesListPage> {
List businessprofileslist = [];
#override
void initState() {
super.initState();
fetchBusinessProfilesList();
}
fetchBusinessProfilesList() async {
dynamic result = await DatabaseManager().GetBusinessProfilesCollection();
print(result.toString());
if (result == null) {
print('enable to retieve');
} else {
print('success');
setState(() {
businessprofileslist = result;
});
}
}
#override
Widget build(BuildContext context) {
return Scaffold();
}
}
You're not returning anything from GetBusinessProfilesCollection but null, so the result seems somewhat expected.
I guess you want to do:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
List businessprofileslist = [];
try {
var QuerySnapshot = await BusinessProfilesCollection.get();
querySnapshot.docs.forEach((element) {
businessprofileslist.add(element.data());
});
return businessprofileslist;
} catch (e) {
print(e.toString());
return null;
}
}
}
Btw: returning null when the load fails, is just going to lead to a null pointer exception when you then do print(result.toString());. So I recommend not catching the error and just letting it bubble up. With that your code can be simplified to:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
var QuerySnapshot = await BusinessProfilesCollection.get();
return querySnapshot.docs.map((element) => element.data());
}
}
You just need to return the list
return businessprofileslist;
CODE :
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
List businessprofileslist = [];
try {
await BusinessProfilesCollection.get().then((QuerySnapshot) {
QuerySnapshot.docs.forEach((element) {
businessprofileslist.add(element.data());
print(businessprofileslist[0]);
});
// you just need to return the list here after filling it up
return businessprofileslist;
});
} catch (e) {
print(e.toString());
return null;
}
}
}
Code with a little improvement:
class DatabaseManager {
final CollectionReference BusinessProfilesCollection =
FirebaseFirestore.instance.collection("BusinessProfilesCollection");
Future GetBusinessProfilesCollection() async {
await BusinessProfilesCollection.get().then((QuerySnapshot) {
QuerySnapshot.docs.map((doc) => doc.data()).toList();
});
}
}
Try that with calling the function in feching
fetchBusinessProfilesList()
async {
dynamic result ;
await DatabaseManager().GetBusinessProfilesCollection().then((value){
result=value;
print(result.toString());
if (result == null) {
print('enable to retieve');
} else {
print('success');
setState(() {
businessprofileslist = result;
});
}
});
}
I working on error handling of api's. i want if api is crashed then it display a message of "Server is down" something like this, in UI.
I created a class where i'm creating methods of api, here in getBooks method if i modify the api url then it is printing this Exception, and i want it in UI. The problem is getBooks return type is List<Book>> so we can't return this Exception, any solution how to do this?
Exception
E/flutter (12924): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Exception
here is my api code
class BooksApi {
static Future<List<Book>> getBooks(String query) async {
try {
final url = Uri.parse(
'https://gist.githubusercontent.com/JohannesMilke/d53fbbe9a1b7e7ca2645db13b995dc6f/raw/eace0e20f86cdde3352b2d92f699b6e9dedd8c70/books.json');
final response = await http.get(url);
if (response.statusCode == 200) {
final List books = json.decode(response.body);
return books.map((json) => Book.fromJson(json)).where((book) {
final titleLower = book.title.toLowerCase();
final authorLower = book.author.toLowerCase();
final searchLower = query.toLowerCase();
return titleLower.contains(searchLower) ||
authorLower.contains(searchLower);
}).toList();
} else {
throw Exception;
}
} catch (e) {
print("e");
print(e);
}
throw Exception;
}
}
and calling it like
Future init() async {
setState(() {
isLoading = true;
});
var books = await BooksApi.getBooks(query); //this
var response = await obj.getProduct();
print(response);
setState(() => this.books = books);
setState(() {
isLoading = false;
});
}
You could handle errors with then and onError :
await BooksApi.getBooks(query).then((books) async {
setState(() => {
this.books = books;
this.isLoading = false;
})
}, onError: (error) {
// do something with error
});
or a simple try-catch (you can write try-catch clauses the same way you would in synchronous code).
See handling errors.
You can also use catchError id you don't use async/await :
BooksApi.getBooks(query).then((books) {
setState(() => {
this.books = books;
this.isLoading = false;
})
}).catchError((error, stackTrace) {
print("error is: $error");
});
See futures error handling.
Try to wrap 'var books = await BooksApi.getBooks(query)' with try and catch.
...
try {
var books = await BooksApi.getBooks(query);
} catch (e) {
// To do for UI
}
...
For api, you need to make something like this:
APIModel{
final int code;
// or a success flag
// final bool success;
final String message;
final List<Book> data;
APIModel({this.code,this.message,this.data});
}
It means, every api have its own code,message,and data filed.
When you request, you can check your code or success:
var response = await request(params);
isLoading = false;
if(response.code == 0){}
// or
if(response.success){
// do what you want
}
else {
Toast.show(response.message);
}
You can use build_runner and json_serializable.
I need a good way to handle errors while I'm Using Dio requests.
Can I do it in one class and pass the dio request throw it ?
and it should return a response with the error .
I am posting my generalized network bloc here, which can be reused any number of time, any where. also, It uses dio using API repository , exceptional and error handling.
class NetworkBloc extends Bloc<NetworkEvent, NetworkState> {
NetworkBloc() : super(NetworkRequestInitial());
#override
Stream<NetworkState> mapEventToState(
NetworkEvent event,
) async* {
yield NetworkRequestInitiated();
if (event is NetworkCallEvent) {
RequestType requestType = event.requestType;
if (requestType == RequestType.GET) {
yield* fetchData(event);
} else if (requestType == RequestType.POST) {
yield* uploadDataAndStoreResult(event);
}
}
}
Stream<NetworkState> fetchData(NetworkCallEvent event) async* {
Response response;
try {
yield NetworkRequestLoading();
response =
await event.apiRepository.sendGetRequest(event.url, event.request);
if (response.statusCode == 200) {
yield NetworkRequestLoaded(response: response);
} else {
Map jsonResponse = jsonDecode(response.data);
yield NetworkRequestFailure(message: jsonResponse['message']);
}
} catch (e) {
yield NetworkRequestFailure(
message: NetworkUtils.getErrorMessageAccordingToError(e));
}
}
Stream<NetworkState> uploadDataAndStoreResult(NetworkCallEvent event) async* {
Response response;
try {
yield NetworkRequestLoading();
if (event.request != null) {
if (event.isHeadersNeeded) {
response = await event.apiRepository.sendPostRequestWithHeader(
event.url,
request: event.request,
);
} else {
response = await event.apiRepository.sendPostRequest(
event.url,
event.request,
);
}
} else {
response = await event.apiRepository
.sendPostRequestWithoutBodyParameters(event.url);
}
if (response.statusCode == 200) {
saveDataAccordingToCacheMechanism(event, response);
yield NetworkRequestLoaded(response: response);
} else {
Map jsonResponse = jsonDecode(response.data);
yield NetworkRequestFailure(message: jsonResponse['message']);
}
} catch (e) {
yield NetworkRequestFailure(
message: NetworkUtils.getErrorMessageAccordingToError(e));
}
}
void saveDataAccordingToCacheMechanism(
NetworkCallEvent event, Response response) async {
if (event.cacheMechanism == CacheMechanism.SharePreferences) {
Hive.box(ConstUtils.dbName)
.put(event.keyForSharedPreferences, response.data.toString());
} else if (event.cacheMechanism == CacheMechanism.Database) {}
}
}
I am also adding states and events to make it more easy to understand.
class NetworkCallEvent extends NetworkEvent {
final String request;
final dynamic url;
final RequestType requestType;
final CacheMechanism cacheMechanism;
final String keyForSharedPreferences;
final APIRepository apiRepository;
final bool isHeadersNeeded;
NetworkCallEvent(
{#required this.url,
this.request,
this.isHeadersNeeded = false,
#required this.requestType,
#required this.apiRepository,
#required this.cacheMechanism,
this.keyForSharedPreferences});
#override
List<Object> get props => [
this.url,
this.request,
this.requestType,
this.cacheMechanism,
this.keyForSharedPreferences,
this.apiRepository
];
}
Network_states:
class NetworkRequestInitial extends NetworkState {}
class NetworkRequestInitiated extends NetworkState {}
class NetworkRequestLoading extends NetworkState {}
class NetworkRequestLoaded extends NetworkState {
final dynamic response;
NetworkRequestLoaded({this.response});
#override
List<Object> get props => [this.response];
}
class NetworkRequestFailure extends NetworkState {
final String message;
NetworkRequestFailure({this.message});
#override
List<Object> get props => [this.message];
}
You can easily send request in JSON and get Response in dynamic, which you can convert to appropriate object using json.decode().
In my flutter app, I have a future that handles http requests and returns the decoded data. But I want to be able to send an error if the status code != 200 that can be gotten with the .catchError() handler.
Heres the future:
Future<List> getEvents(String customerID) async {
var response = await http.get(
Uri.encodeFull(...)
);
if (response.statusCode == 200){
return jsonDecode(response.body);
}else{
// I want to return error here
}
}
and when I call this function, I want to be able to get the error like:
getEvents(customerID)
.then(
...
).catchError(
(error) => print(error)
);
Throwing an error/exception:
You can use either return or throw to throw an error or an exception.
Using return:
Future<void> foo() async {
if (someCondition) {
return Future.error('FooError');
}
}
Using throw:
Future<void> bar() async {
if (someCondition) {
throw Exception('BarException');
}
}
Catching the error/exception:
You can use either catchError or try-catch block to catch the error or the exception.
Using catchError:
foo().catchError(print);
Using try-catch:
try {
await bar();
} catch (e) {
print(e);
}
You can use throw :
Future<List> getEvents(String customerID) async {
var response = await http.get(
Uri.encodeFull(...)
);
if (response.statusCode == 200){
return jsonDecode(response.body);
}else{
// I want to return error here
throw("some arbitrary error"); // error thrown
}
}
Another way to solve this is by using the dartz package.
An example of how to use it would look something similar like this
import 'package:dartz/dartz.dart';
abstract class Failure {}
class ServerFailure extends Failure {}
class ResultFailure extends Failure {
final int statusCode;
const ResultFailure({required this.statusCode});
}
FutureOr<Either<Failure, List>> getEvents(String customerID) async {
try {
final response = await http.get(
Uri.encodeFull(...)
);
if (response.statusCode == 200) {
return Right(jsonDecode(response.body));
} else {
return Left(ResultFailure(statusCode: response.statusCode));
}
}
catch (e) {
return Left(ServerFailure());
}
}
main() async {
final result = await getEvents('customerId');
result.fold(
(l) => print('Some failure occurred'),
(r) => print('Success')
);
}
You can return the error data like this if you want to read the error object:
response = await dio.post(endPoint, data: data).catchError((error) {
return error.response;
});
return response;
//POST
Future<String> post_firebase_async({String? path , required Product product}) async {
final Uri _url = path == null ? currentUrl: Uri.https(_baseUrl, '/$path');
print('Sending a POST request at $_url');
final response = await http.post(_url, body: jsonEncode(product.toJson()));
if(response.statusCode == 200){
final result = jsonDecode(response.body) as Map<String,dynamic>;
return result['name'];
}
else{
//throw HttpException(message: 'Failed with ${response.statusCode}');
return Future.error("This is the error", StackTrace.fromString("This is its trace"));
}
}
Here is how to call:
final result = await _firebase.post_firebase_async(product: dummyProduct).
catchError((err){
print('huhu $err');
});