[英]Can't initialized GraphQl Client in flutter using Get_it
我想在我的 Flutter 應用程序中實現 GraphQL 客戶端。 對於依賴注入,我使用 GetIt 庫。 但是當我運行應用程序時,它說
'無效參數(HomeGraphQLService 類型的對象未在 GetIt 中注冊。您是否忘記傳遞實例名稱?(您是否不小心執行了 GetIt sl=GetIt.instance(); 而不是 GetIt sl=GetIt.instance;)):HomeGraphQLService '
.
這意味着 GraphQL 客戶端沒有以某種方式實例化,盡管我在我的服務定位器中注冊了它
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());
}
我不能說它到底發生在哪里,因為它在您訪問GraphQLService
代碼中的其他地方,但問題肯定是由於延遲加載造成的。 在訪問對象之前, locator
尚未創建和加載該對象。 嘗試更新ServiceLocator.dart
以在注冊期間實例化類,如下所示:
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()));
}
給你:我不能說它到底發生在哪里,因為它在你訪問 GraphQLService 的代碼中的其他地方,但問題肯定是由於延遲加載造成的。 在訪問對象之前,定位器尚未創建和加載該對象。 嘗試更新 ServiceLocator.dart 以在注冊期間實例化類,如下所示:
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()));
}```
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