인프런 커뮤니티 질문&답변

안녕하세요~ 덕분에 클린 아키텍쳐 구조 잘 공부했습니다.

혹시 의존성 주입부분에서 질문이 있습니다.

제가 개인적으로 연습을 하면서 클린 아키텍쳐를 적용하고 있습니다.

1. /di/provider_setup.dart 에서 한번에 의존성 주입

List<ChangeNotifierProvider> getProviders() {
  final dio = Dio();

  SongRepository repository = SongRepository(dio);

  UseCases useCases = UseCases(
    getSearchSong: GetSearchSongUseCase(repository: repository),
    getSearchSinger: GetSearchSingerUseCase(repository: repository),
    getRecentlySongsList: GetRecentlySongsListUseCase(repository:repository),
  );

  SearchViewModel searchViewModel = SearchViewModel(useCases: useCases);
  HomeViewModel homeViewModel = HomeViewModel(useCases: useCases);

  return [
    ChangeNotifierProvider(create: (_) => searchViewModel),
    ChangeNotifierProvider(create: (_) => homeViewModel),
  ];
}

2. main 에서 주입

void main() {
  // provider 호출
  final providers = getProviders();

  runApp(
    MultiProvider(
      providers: providers,
      child: const MyApp(),
    ),
  );
}

3. context.watch<SearchViewModel>(); 은 잘 작동해서 뷰에 출력을 잘 하고있습니다.

   class _SearchScreenState extends State<SearchScreen> {
   
     @override
     Widget build(BuildContext context) {
       final searchViewModel = context.watch<SearchViewModel>();
       final state = searchViewModel.state;
       ...
   }

4. context.watch<HomeViewModel>();은 에러가 발생합니다.

   class _Body extends StatelessWidget {
     const _Body({Key? key}) : super(key: key);
   
     @override
     Widget build(BuildContext context) {
       final homeViewModel = context.watch<HomeViewModel>();
       final state = homeViewModel.state;
       ...
   }

에러내용

======== Exception caught by widgets library =======================================================
The following ProviderNotFoundException was thrown building _Body(dirty):
Error: Could not find the correct Provider<HomeViewModel> above this _Body Widget

This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:

- You added a new provider in your `main.dart` and performed a hot-reload.
  To fix, perform a hot-restart.

- The provider you are trying to read is in a different route.

  Providers are "scoped". So if you insert of provider inside a route, then
  other routes will not be able to access that provider.

- You used a `BuildContext` that is an ancestor of the provider you are trying to read.

  Make sure that _Body is under your MultiProvider/Provider<HomeViewModel>.
  This usually happens when you are creating a provider and trying to read it immediately.

  For example, instead of:

  ```
  Widget build(BuildContext context) {
    return Provider<Example>(
      create: (_) => Example(),
      // Will throw a ProviderNotFoundError, because `context` is associated
      // to the widget that is the parent of `Provider<Example>`
      child: Text(context.watch<Example>().toString()),
    );
  }
  ```

  consider using `builder` like so:

  ```
  Widget build(BuildContext context) {
    return Provider<Example>(
      create: (_) => Example(),
      // we use `builder` to obtain a new `BuildContext` that has access to the provider
      builder: (context, child) {
        // No longer throws
        return Text(context.watch<Example>().toString());
      }
    );
  }
  ```

If none of these solutions work, consider asking for help on StackOverflow:
https://stackoverflow.com/questions/tagged/flutter

The relevant error-causing widget was: 
When the exception was thrown, this was the stack: 
#0      Provider._inheritedElementOf (package:provider/src/provider.dart:343:7)
#1      Provider.of (package:provider/src/provider.dart:293:30)
#2      WatchContext.watch (package:provider/src/provider.dart:693:21)
#3      _Body.build (package:what_do_you_want_to_sing/presentation/home/home_screen.dart:79:35)
#4      StatelessElement.build (package:flutter/src/widgets/framework.dart:4949:49)
#5      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4878:15)
#6      Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#7      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2667:19)
#8      WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:882:21)
#9      RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:378:5)
#10     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1175:15)
#11     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1104:9)
#12     SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:881:7)
(elided 4 frames from class _RawReceivePortImpl, class _Timer, and dart:async-patch)

저번에 이런 에러가 발생했을때, 의존성 주입이 안된 상태에서 context.watch() 를 해서 오류가 나 의존성을 추가해 해결했습니다.

하지만 이번에는 잘모르겠습니다. 의존성도 잘 주입되어서 view 단에서 잘 호출 하고 있는거 같은데.. 어떻게 해결해야할까요?