refactor: MainViewCoordinator 하위 화면 ViewModel 보관 방식 단순화

MainViewCoordinator가 생성하는 하위 화면 ViewModel을 단일 인스턴스 기준으로 보관하도록 변경

- TodoListViewModel은 현재 category와 일치할 때 기존 인스턴스 재사용
- TodoDetailViewModel은 현재 todoId와 showEditButton 조건이 일치할 때 기존 인스턴스 재사용
- category별 dictionary와 todoId별 dictionary 제거
- ViewModel이 가진 생성 기준 값을 재사용 조건으로 활용하여 코디네이터의 별도 key 상태 제거
- compact/regular 전환으로 같은 하위 화면이 재생성될 때 기존 ViewModel 인스턴스를 유지하는 구조

Author: opficdev

DevLog/Presentation/ViewModel/TodoDetailViewModel.swift

@@ -40,11 +40,11 @@ final class TodoDetailViewModel: Store {
     }
 
     private(set) var state: State = .init()
+    let todoId: String
     let showEditButton: Bool
     private let fetchTodoUseCase: FetchTodoByIdUseCase
     private let fetchReferenceItemsUseCase: FetchReferenceItemsUseCase
     private let upsertUseCase: UpsertTodoUseCase
-    private let todoId: String
     private let loadingState = LoadingState()
 
     init(

DevLog/Presentation/ViewModel/TodoListViewModel.swift

@@ -114,6 +114,10 @@ final class TodoListViewModel: Store {
 
     let searchResultsLimit = 5
 
+    var category: TodoCategory {
+        state.category
+    }
+
     var appliedFilterCount: Int {
         var count = 0
         if state.query.sortTarget != .createdAt { count += 1 }

DevLog/UI/Main/MainViewCoordinator.swift

@@ -16,9 +16,9 @@ final class MainViewCoordinator {
     var todoIdToPresent: TodoIdItem?
     private let diContainer: DIContainer
     @ObservationIgnored
-    private var todoListViewModels = [TodoCategory: TodoListViewModel]()
+    private var todoListViewModel: TodoListViewModel?
     @ObservationIgnored
-    private var todoDetailViewModels = [TodoDetailViewModelKey: TodoDetailViewModel]()
+    private var todoDetailViewModel: TodoDetailViewModel?
 
     init(container: DIContainer) {
         self.diContainer = container
@@ -44,7 +44,8 @@ final class MainViewCoordinator {
     }
 
     func todoListViewModel(category: TodoCategory) -> TodoListViewModel {
-        if let todoListViewModel = todoListViewModels[category] {
+        if let todoListViewModel,
+           todoListViewModel.category == category {
             return todoListViewModel
         }
 
@@ -56,19 +57,17 @@ final class MainViewCoordinator {
             undoDeleteTodoUseCase: diContainer.resolve(UndoDeleteTodoUseCase.self),
             category: category
         )
-        todoListViewModels[category] = todoListViewModel
+        self.todoListViewModel = todoListViewModel
         return todoListViewModel
     }
 
     func todoDetailViewModel(
         todoId: String,
         showEditButton: Bool = true
     ) -> TodoDetailViewModel {
-        let todoDetailViewModelKey = TodoDetailViewModelKey(
-            todoId: todoId,
-            showEditButton: showEditButton
-        )
-        if let todoDetailViewModel = todoDetailViewModels[todoDetailViewModelKey] {
+        if let todoDetailViewModel,
+           todoDetailViewModel.todoId == todoId,
+           todoDetailViewModel.showEditButton == showEditButton {
             return todoDetailViewModel
         }
 
@@ -79,12 +78,7 @@ final class MainViewCoordinator {
             todoId: todoId,
             showEditButton: showEditButton
         )
-        todoDetailViewModels[todoDetailViewModelKey] = todoDetailViewModel
+        self.todoDetailViewModel = todoDetailViewModel
         return todoDetailViewModel
     }
-
-    private struct TodoDetailViewModelKey: Hashable {
-        let todoId: String
-        let showEditButton: Bool
-    }
 }