Can't initialized GraphQl Client in flutter using Get_it - flutter

Question

I want to implement GraphQL client in my flutter app. For Dependency injection, I use GetIt library. But when I run the app, it says
'Invalid argument (Object of type HomeGraphQLService is not
registered inside GetIt. Did you forget to pass an instance name?
(Did you accidentally do GetIt sl=GetIt.instance(); instead of GetIt
sl=GetIt.instance;)): HomeGraphQLService'
.
It means GraphQL client did not instantiate somehow, although I registered it in my service locator
Session.dart
abstract class Session {
String getAccessToken();
}
SessionImpl.dart
class SessionImpl extends Session {
SharedPreferences sharedPref;
SessionImpl(SharedPreferences sharedPref) {
this.sharedPref = sharedPref;
}
#override
String getAccessToken() {
return sharedPref.getString('access_token') ?? "";
}
}
GraphQLClientGenerator.dart
class GraphQLClientGenerator {
Session session;
GraphQLClientGenerator(Session session) {
this.session = session;
}
GraphQLClient getClient() {
final HttpLink httpLink = HttpLink('https://xxx/graphql');
final AuthLink authLink = AuthLink(getToken: () async => 'Bearer ${_getAccessToken()}');
final Link link = authLink.concat(httpLink);
return GraphQLClient(link: link, cache: GraphQLCache(store: InMemoryStore()));
}
String _getAccessToken() {
return session.getAccessToken();
}
}
HomeRepository.dart
abstract class HomeRepository {
Future<List<Course>> getAllCourseOf(String className, String groupName);
}
HomeRepositoryImpl.dart
class HomeRepositoryImpl extends HomeRepository {
HomeGraphQLService homeGraphQLService;
HomeMapper homeMapper;
HomeRepositoryImpl(HomeGraphQLService homeGraphQLService, HomeMapper homeMapper) {
this.homeGraphQLService = homeGraphQLService;
this.homeMapper = homeMapper;
}
#override
Future<List<Course>> getAllCourseOf(String className, String groupName) async {
final response = await homeGraphQLService.getAllCourseOf(className, groupName);
return homeMapper.toCourses(response).where((course) => course.isAvailable);
}
}
HomeGraphQLService.dart
class HomeGraphQLService {
GraphQLClient graphQLClient;
HomeGraphQLService(GraphQLClient graphQLClient) {
this.graphQLClient = graphQLClient;
}
Future<SubjectResponse> getAllCourseOf(String className, String groupName) async {
try {
final response = await graphQLClient.query(getAllCourseQuery(className, groupName));
return SubjectResponse.fromJson((response.data));
} catch (e) {
return Future.error(e);
}
}
}
GraphQuery.dart
QueryOptions getAllCourseQuery(String className, String groupName) {
String query = """
query GetSubject($className: String, $groupName: String) {
subjects(class: $className, group: $groupName) {
code
display
insights {
coming_soon
purchased
}
}
}
""";
return QueryOptions(
document: gql(query),
variables: <String, dynamic>{
'className': className,
'groupName': groupName,
},
);
}
ServiceLocator.dart
final serviceLocator = GetIt.instance;
Future<void> initDependencies() async {
await _initSharedPref();
_initSession();
_initGraphQLClient();
_initGraphQLService();
_initMapper();
_initRepository();
}
Future<void> _initSharedPref() async {
SharedPreferences sharedPref = await SharedPreferences.getInstance();
serviceLocator.registerSingleton<SharedPreferences>(sharedPref);
}
void _initSession() {
serviceLocator.registerLazySingleton<Session>(()=>SessionImpl(serviceLocator()));
}
void _initGraphQLClient() {
serviceLocator.registerLazySingleton<GraphQLClient>(() => GraphQLClientGenerator(serviceLocator()).getClient());
}
void _initGraphQLService() {
serviceLocator.registerLazySingleton<HomeGraphQLService>(() => HomeGraphQLService(serviceLocator()));
}
void _initMapper() {
serviceLocator.registerLazySingleton<HomeMapper>(() => HomeMapper());
}
void _initRepository() {
serviceLocator.registerLazySingleton<HomeRepository>(() => HomeRepositoryImpl(serviceLocator(), serviceLocator()));
}
main.dart
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations(
[DeviceOrientation.portraitUp, DeviceOrientation.portraitDown],
);
await initDependencies();
runApp(MyApp());
}

Answer 1

I cannot say where exactly it is happening because it is elsewhere in your code where you are accessing the GraphQLService, but the problem is definitely due to the lazy loading. The object has not been created and loaded by the locator before it is being accessed. Try updating ServiceLocator.dart to instantiate the classes during registration, like so:
void _initSession() {
serviceLocator.registerSingleton<Session>.(SessionImpl(serviceLocator()));
}
void _initGraphQLClient() {
serviceLocator.registerSingleton<GraphQLClient>(
GraphQLClientGenerator(serviceLocator()).getClient());
}
void _initGraphQLService() {
serviceLocator.registerSingleton<HomeGraphQLService>(
HomeGraphQLService(serviceLocator()));
}
void _initMapper() {
serviceLocator.registerSingleton<HomeMapper>(HomeMapper());
}
void _initRepository() {
serviceLocator.registerSingleton<HomeRepository>(
HomeRepositoryImpl(serviceLocator(), serviceLocator()));
}