add native examples

todo-swiftui/TodoSwiftUI/ViewModels/TodoViewModel.swift

@@ -0,0 +1,84 @@
+import Foundation
+import SwiftUI
+
+@Observable
+final class TodoViewModel {
+    var todos: [Todo] = []
+    var currentFilter: TodoFilter = .all
+
+    // MARK: - Computed Properties
+
+    var filteredTodos: [Todo] {
+        switch currentFilter {
+        case .all:
+            return todos
+        case .active:
+            return todos.filter { !$0.completed }
+        case .done:
+            return todos.filter { $0.completed }
+        }
+    }
+
+    var allCount: Int {
+        todos.count
+    }
+
+    var activeCount: Int {
+        todos.filter { !$0.completed }.count
+    }
+
+    var doneCount: Int {
+        todos.filter { $0.completed }.count
+    }
+
+    func count(for filter: TodoFilter) -> Int {
+        switch filter {
+        case .all: return allCount
+        case .active: return activeCount
+        case .done: return doneCount
+        }
+    }
+
+    // MARK: - Initialization
+
+    init() {
+        loadTodos()
+    }
+
+    // MARK: - Actions
+
+    func loadTodos() {
+        todos = DatabaseManager.shared.loadTodos()
+    }
+
+    func addTodo(title: String, category: String, priority: Priority) {
+        if let todo = DatabaseManager.shared.insertTodo(title: title, category: category, priority: priority) {
+            todos.insert(todo, at: 0)
+        }
+    }
+
+    func updateTodo(id: Int64, title: String, category: String, priority: Priority) {
+        DatabaseManager.shared.updateTodo(id: id, title: title, category: category, priority: priority)
+        if let index = todos.firstIndex(where: { $0.id == id }) {
+            todos[index].title = title
+            todos[index].category = category
+            todos[index].priority = priority
+        }
+    }
+
+    func toggleTodo(id: Int64) {
+        if let index = todos.firstIndex(where: { $0.id == id }) {
+            todos[index].completed.toggle()
+            DatabaseManager.shared.toggleTodo(id: id, completed: todos[index].completed)
+        }
+    }
+
+    func deleteTodo(id: Int64) {
+        DatabaseManager.shared.deleteTodo(id: id)
+        todos.removeAll { $0.id == id }
+    }
+
+    func setFilter(_ filter: TodoFilter) {
+        currentFilter = filter
+    }
+}