Task deletion feature (#7)

This PR contains the work done to add support for todo tasks deletion on the *Task list* view.

Reviewed-on: rock-n-code/todos-app#7
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/View Models/TaskListViewModel.swift

@@ -1,3 +1,4 @@
+import Foundation
 import SwiftData
 import SwiftUI
 
@@ -84,6 +85,26 @@ extension TaskListView {
 
         // MARK: Methods
 
+        /// Deletes tasks at the specified indices.
+        ///
+        /// This method removes tasks from the model context after a swipe-to-delete action.
+        /// The deletion is performed through SwiftData's model context, which handles
+        /// persistence and triggers automatic UI updates.
+        ///
+        /// - Parameters:
+        ///   - tasks: The current array of tasks.
+        ///   - offsets: The index set of tasks to delete.
+        ///   - modelContext: The SwiftData model context to perform the deletion.
+        func deleteTasks(
+            _ tasks: [Todo],
+            at offsets: IndexSet,
+            from modelContext: ModelContext
+        ) {
+            for index in offsets {
+                modelContext.delete(tasks[index])
+            }
+        }
+
         /// Reorders tasks after a drag and drop operation.
         ///
         /// This method is called when users drag and drop tasks to reorder them within a group.

App/Sources/Views/TaskList/TaskListContent.swift

@@ -18,17 +18,24 @@ extension TaskListView {
 
         // MARK: Type aliases
 
+        /// Closure type for handling task deletion operations.
+        ///
+        /// - Parameters:
+        ///   - todos: The current array of todo tasks.
+        ///   - offsets: The index set of tasks to delete.
+        typealias DeleteClosure = ([Todo], IndexSet) -> Void
+
         /// Closure type for handling task reorder operations.
         ///
         /// - Parameters:
-        ///   - tasks: The current array of tasks.
+        ///   - todos: The current array of todo tasks.
         ///   - source: The index set of items being moved.
         ///   - destination: The destination index for the moved items.
         typealias ReorderClosure = ([Todo], IndexSet, Int) -> Void
 
         // MARK: Properties
 
-        /// Query to fetch todos filtered by group and completion status.
+        /// Query to fetch todo tasks filtered by group and completion status.
         ///
         /// This query is initialized with a todo fetch descriptor that applies predicates
         /// based on the group type and completion filter. SwiftData automatically
@@ -37,7 +44,7 @@ extension TaskListView {
         /// Tasks are sorted by their `order` property first, then by date-based criteria
         /// specific to each group, enabling both manual and automatic ordering.
         @Query
-        private var tasks: [Todo]
+        private var todos: [Todo]
 
         /// Indicates whether tasks in this view can be reordered through drag and drop.
         ///
@@ -45,6 +52,12 @@ extension TaskListView {
         /// determines whether the `.onMove` modifier is applied to the task list.
         private let canReorder: Bool
 
+        /// Closure called when tasks are deleted through swipe-to-delete.
+        ///
+        /// This closure is invoked by the `.onDelete` modifier and is responsible for
+        /// removing the selected tasks from the model context.
+        private let onDelete: DeleteClosure
+
         /// Closure called when tasks are reordered through drag and drop.
         ///
         /// This closure is invoked by the `.onMove` modifier and is responsible for
@@ -67,12 +80,14 @@ extension TaskListView {
         ///   - group: The todo group category to filter by (today, upcoming, overdue, or completed).
         ///   - showCompleted: Whether to include completed tasks in the results. Only applies to groups other than `.completed`.
         ///   - onReorder: A closure called when tasks are reordered.
+        ///   - onDelete: A closure called when tasks are deleted.
         init(
             group: TodoGroup,
             showCompleted: Bool,
+            onDelete: @escaping DeleteClosure,
             onReorder: @escaping ReorderClosure
         ) {
-            self._tasks = .init(
+            self._todos = .init(
                 FetchDescriptor<Todo>(
                     group: group,
                     showCompleted: showCompleted
@@ -80,6 +95,7 @@ extension TaskListView {
             )
 
             self.canReorder = group.canReorder
+            self.onDelete = onDelete
             self.onReorder = onReorder
         }
 
@@ -97,7 +113,7 @@ extension TaskListView {
         /// in read-only mode with chronological sorting.
         var body: some View {
             Group {
-                if tasks.isEmpty {
+                if todos.isEmpty {
                     ContentUnavailableView(
                         "view.task-list-content.content-unavailable.title",
                         systemImage: "checkmark.circle"
@@ -105,19 +121,7 @@ extension TaskListView {
                 }
                 else {
                     List {
-                        if canReorder {
+                        items
-                            ForEach(tasks) {
-                                TaskListView.Item($0)
-                            }
-                            .onMove { source, destination in
-                                onReorder(tasks, source, destination)
-                            }
-                        }
-                        else {
-                            ForEach(tasks) {
-                                TaskListView.Item($0)
-                            }
-                        }
                     }
                     .listStyle(.grouped)
                 }
@@ -127,6 +131,34 @@ extension TaskListView {
 
 }
 
+// MARK: - Helpers
+
+private extension TaskListView.Content {
+
+    // MARK: Computed
+
+    /// A view that renders the task items with appropriate modifiers.
+    @ViewBuilder
+    var items: some View {
+        let items = ForEach(todos) {
+            TaskListView.Item($0)
+        }
+        .onDelete { offsets in
+            onDelete(todos, offsets)
+        }
+
+        if canReorder {
+            items.onMove { source, destination in
+                onReorder(todos, source, destination)
+            }
+        }
+        else {
+            items
+        }
+    }
+
+}
+
 // MARK: - Previews
 
 #Preview(
@@ -136,7 +168,9 @@ extension TaskListView {
     TaskListView.Content(
         group: .today,
         showCompleted: .random()
-    ) { _, _, _ in
+    ) { _, _ in
+        // On delete closure
+    } onReorder: { _, _, _ in
         // On reorder closure
     }
 }
@@ -148,7 +182,9 @@ extension TaskListView {
     TaskListView.Content(
         group: .today,
         showCompleted: false
-    ) { _, _, _ in
+    ) { _, _ in
+        // On delete closure
+    } onReorder: { _, _, _ in
         // On reorder closure
     }
 }
@@ -160,7 +196,9 @@ extension TaskListView {
     TaskListView.Content(
         group: .today,
         showCompleted: true
-    ) { _, _, _ in
+    ) { _, _ in
+        // On delete closure
+    } onReorder: { _, _, _ in
         // On reorder closure
     }
 }
@@ -172,7 +210,9 @@ extension TaskListView {
     TaskListView.Content(
         group: .completed,
         showCompleted: .random()
-    ) { _, _, _ in
+    ) { _, _ in
+        // On delete closure
+    } onReorder: { _, _, _ in
         // On reorder closure
     }
 }

App/Sources/Views/TaskListView.swift

@@ -9,6 +9,10 @@ struct TaskListView: View {
 
     // MARK: Properties
 
+    /// The SwiftData model context for performing data operations.
+    @Environment(\.modelContext)
+    private var modelContext
+
     /// The view model managing the state and business logic for this view.
     ///
     /// This view model holds the group configuration and completion filter state.
@@ -40,8 +44,18 @@ struct TaskListView: View {
         Content(
             group: viewModel.group,
             showCompleted: viewModel.showCompleted
-        ) { tasks, source, destination in
+        ) { tasks, offsets in
-            viewModel.reorderTasks(tasks, from: source, to: destination)
+            viewModel.deleteTasks(
+                tasks,
+                at: offsets,
+                from: modelContext
+            )
+        } onReorder: { tasks, source, destination in
+            viewModel.reorderTasks(
+                tasks,
+                from: source,
+                to: destination
+            )
         }
         .navigationTitle(viewModel.navigationTitle)
         .toolbar {

UnitTests/Tests/View Models/TaskListViewModelTests.swift

@@ -91,6 +91,45 @@ struct TaskListViewModelTests {
 
     // MARK: Method tests
 
+    @Test("deleteTasks removes a single task from model context")
+    func deleteTasksSingle() throws {
+        // GIVEN
+        let container = try ModelContainer(
+            for: Todo.self,
+            configurations: .init(isStoredInMemoryOnly: true)
+        )
+        let context = ModelContext(container)
+
+        let viewModel = TaskListView.ViewModel(group: .today)
+        let todosToInsert: [Todo] = [
+            .init(title: "Task 1", due: .now, order: 0),
+            .init(title: "Task 2", due: .now, order: 1),
+            .init(title: "Task 3", due: .now, order: 2),
+        ]
+        let countInitial = todosToInsert.count
+
+        for todo in todosToInsert {
+            context.insert(todo)
+        }
+
+        // WHEN
+        viewModel.deleteTasks(
+            todosToInsert,
+            at: IndexSet(integer: 1),
+            from: context
+        )
+
+        // THEN
+        let descriptor = FetchDescriptor<Todo>()
+        let todos = try context.fetch(descriptor)
+
+        #expect(countInitial == 3)
+        #expect(todos.count == 2)
+        #expect(todos.contains(where: { $0.title == "Task 1" }))
+        #expect(todos.contains(where: { $0.title == "Task 3" }))
+        #expect(!todos.contains(where: { $0.title == "Task 2" }))
+    }
+
     @Test("reorderTasks updates order property when moving task forward")
     func reorderTasksMovingForward() {
         // GIVEN