App/Sources/View Models/TaskGroupListViewModel.swift

@@ -45,41 +45,42 @@ extension TaskGroupListView {
 
         // MARK: Functions
 
-        /// Calculates the number of tasks for a given task group using SwiftData.
+        /// Calculates the number of tasks for a given task group from an in-memory collection.
         ///
-        /// This method performs an efficient database-level count using SwiftData's `fetchCount` method with predicate-based filtering.
+        /// This method filters the provided tasks array to count only those tasks that belong
-        /// Tasks are categorized based on their due date and completion status.
+        /// to the specified group based on their due date and completion status. Tasks are
+        /// categorized as follows:
+        ///
+        /// - **Completed**: Tasks with a non-nil `completed` date
+        /// - **Overdue**: Incomplete tasks due before today
+        /// - **Today**: Incomplete tasks due today (from start of day to end of day)
+        /// - **Upcoming**: Incomplete tasks due tomorrow or later
         ///
         /// - Parameters:
+        ///   - tasks: The array of tasks to filter and count.
         ///   - group: The task group to count tasks for.
-        ///   - modelContext: The SwiftData model context to query.
+        /// - Returns: The number of tasks in the specified group.
-        /// - Returns: The number of tasks in the specified group, or 0 if an error occurs.
         func count(
-            for group: TodoGroup,
+            _ tasks: [Todo],
-            in modelContext: ModelContext
+            for group: TodoGroup
         ) -> Int {
             let today = calendar.startOfDay(for: .now)
             let tomorrow = calendar.date(byAdding: .day, value: 1, to: today) ?? .now
 
-            let fetchDescriptor: FetchDescriptor<Todo> =
+            return tasks
+                .filter { task in
                     switch group {
                         case .completed:
-                        .init(predicate: #Predicate { $0.completed != nil })
+                            task.completed != nil
                         case .overdue:
-                        .init(predicate: #Predicate { $0.completed == nil && $0.due < today })
+                            task.completed == nil && task.due < today
                         case .today:
-                        .init(predicate: #Predicate { $0.completed == nil && $0.due >= today && $0.due < tomorrow })
+                            task.completed == nil && task.due >= today && task.due < tomorrow
                         case .upcoming:
-                        .init(predicate: #Predicate { $0.completed == nil && $0.due >= tomorrow })
+                            task.completed == nil && task.due >= tomorrow
                     }
-
-            do {
-                return try modelContext.fetchCount(fetchDescriptor)
-            }
-            catch {
-                print("Error fetching count for group \(group): \(error)")
-                return 0
                 }
+                .count
         }
 
     }

App/Sources/Views/TaskGroupListView.swift

@@ -12,11 +12,12 @@ struct TaskGroupListView: View {
 
     // MARK: Properties
 
-    /// The SwiftData model context for database operations.
+    /// Query to monitor all todo tasks for changes.
     ///
-    /// This context is used by the view model to perform efficient database-level queries for counting tasks in each group.
+    /// This query triggers view updates whenever todo tasks are inserted, updated, or deleted,
-    @Environment(\.modelContext)
+    /// ensuring the task counts displayed in the view remain accurate.
-    private var modelContext
+    @Query
+    private var tasks: [Todo]
 
     /// The view model managing the state and logic for this view.
     ///
@@ -43,10 +44,7 @@ struct TaskGroupListView: View {
                     NavigationLink(destination: TaskListView(group: group)) {
                         Card(
                             group: group,
-                            count: viewModel.count(
+                            count: viewModel.count(tasks, for: group)
-                                for: group,
-                                in: modelContext
-                            )
                         )
                     }
                     .buttonStyle(.plain)

UnitTests/Tests/View Models/TaskGroupListViewModelTests.swift

@@ -31,58 +31,49 @@ struct TaskGroupListViewModelTests {
 
     // MARK: Functions tests
 
-    @MainActor
     @Test(
         "count returns zero when empty data",
         arguments: TodoGroup.allCases
     )
     func countWhenEmptyData(for group: TodoGroup) throws {
         // GIVEN
-        let container = try ModelContainer(
+        let tasks: [Todo] = []
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
         let viewModel = TaskGroupListView.ViewModel()
 
         // WHEN
-        let count = viewModel.count(for: group, in: container.mainContext)
+        let count = viewModel.count(tasks, for: group)
 
         // THEN
         #expect(count == 0)
     }
 
-    @MainActor
     @Test(
         "count returns correct count when filled data",
         arguments: TodoGroup.allCases
     )
     func countWhenFilledData(for group: TodoGroup) throws {
         // GIVEN
-        let container = try ModelContainer(
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
-        let context = container.mainContext
-
         let today: Date = .now
         let tomorrow = calendar.date(byAdding: .day, value: 1, to: today) ?? today
         let yesterday = calendar.date(byAdding: .day, value: -1, to: today) ?? today
         let nextWeek = calendar.date(byAdding: .day, value: 7, to: today) ?? today
         let lastWeek = calendar.date(byAdding: .day, value: -7, to: today) ?? today
 
-        context.insert(Todo(title: "Today task #1", due: today))
+        let tasks = [
-        context.insert(Todo(title: "Today task #2", due: today))
+            Todo(title: "Today task #1", due: today),
-        context.insert(Todo(title: "Tomorrow task #1", due: tomorrow))
+            Todo(title: "Today task #2", due: today),
-        context.insert(Todo(title: "Next week task #1", due: nextWeek))
+            Todo(title: "Tomorrow task #1", due: tomorrow),
-        context.insert(Todo(title: "Yesterday task #1", due: yesterday))
+            Todo(title: "Next week task #1", due: nextWeek),
-        context.insert(Todo(title: "Last week task #1", due: lastWeek))
+            Todo(title: "Yesterday task #1", due: yesterday),
-        context.insert(Todo(title: "Completed task #1", due: tomorrow, completed: today))
+            Todo(title: "Last week task #1", due: lastWeek),
-        context.insert(Todo(title: "Completed task #2", due: yesterday, completed: today))
+            Todo(title: "Completed task #1", due: tomorrow, completed: today),
+            Todo(title: "Completed task #2", due: yesterday, completed: today)
+        ]
 
         let viewModel = TaskGroupListView.ViewModel()
 
         // WHEN
-        let count = viewModel.count(for: group, in: context)
+        let count = viewModel.count(tasks, for: group)
 
         // THEN
         #expect(count == 2)