Observable Macro for SwiftUI Data Models

 import SwiftUI
−import Combine
+import Observation
 
−class CartItemLegacy: ObservableObject, Identifiable {
+@Observable
+final class CartItem: Identifiable {
     let id = UUID()
−    @Published var name: String
−    @Published var quantity: Int
−    @Published var pricePerUnit: Double
+    var name: String
+    var quantity: Int
+    var pricePerUnit: Double
 
     var totalPrice: Double { Double(quantity) * pricePerUnit }
 
     init(name: String, quantity: Int, pricePerUnit: Double) {
         self.name = name
         self.quantity = quantity
         self.pricePerUnit = pricePerUnit
     }
 }
 
−class CartViewModelLegacy: ObservableObject {
−    @Published var items: [CartItemLegacy] = [
−        CartItemLegacy(name: "Apple", quantity: 3, pricePerUnit: 0.99),
−        CartItemLegacy(name: "Bread", quantity: 1, pricePerUnit: 2.49),
−        CartItemLegacy(name: "Milk", quantity: 2, pricePerUnit: 1.79)
+@Observable
+@MainActor
+final class CartViewModel {
+    var items: [CartItem] = [
+        CartItem(name: "Apple", quantity: 3, pricePerUnit: 0.99),
+        CartItem(name: "Bread", quantity: 1, pricePerUnit: 2.49),
+        CartItem(name: "Milk", quantity: 2, pricePerUnit: 1.79)
     ]
 
     var grandTotal: Double { items.reduce(0) { $0 + $1.totalPrice } }
 
     func removeItems(at offsets: IndexSet) {
         items.remove(atOffsets: offsets)
     }
 }
 
−struct CartItemRowLegacy: View {
−    // Requires @ObservedObject — cannot use simple property reference
−    @ObservedObject var item: CartItemLegacy
+struct CartItemRow: View {
+    @Bindable var item: CartItem
 
     var body: some View {
         HStack {
             Text(item.name)
                 .frame(maxWidth: .infinity, alignment: .leading)
             Stepper("\(item.quantity)", value: $item.quantity, in: 1...99)
             Text(String(format: "$%.2f", item.totalPrice))
                 .frame(width: 60, alignment: .trailing)
                 .foregroundStyle(.secondary)
         }
     }
 }
 
−struct ShoppingCartViewLegacy: View {
−    // Must use @StateObject, not @State, for reference types
−    @StateObject private var cart = CartViewModelLegacy()
+struct ShoppingCartView: View {
+    @State private var cart = CartViewModel()
 
     var body: some View {
         NavigationStack {
             List {
                 ForEach(cart.items) { item in
−                    CartItemRowLegacy(item: item)
+                    CartItemRow(item: item)
                 }
                 .onDelete(perform: cart.removeItems)
             }
             .navigationTitle("Cart")
+            .toolbar {
+                ToolbarItem(placement: .bottomBar) {
+                    Text(String(format: "Total: $%.2f", cart.grandTotal))
+                        .font(.headline)
+                }
+            }
         }
     }
+}
+
+#Preview {
+    ShoppingCartView()
 }