Creating a shopping cart application with MobX

Create a new Flutter application named cart_mobx and copy item.dart into your lib folder, as we have been doing in the previous sections. Add dependencies for equitable, flutter_mobx, and mobx under dependencies inside pubspec.yaml. Also, add dependencies for build_runner and mobx_codegen under dev_dependencies in pubspec.yaml. Let's get started, as follows:

1. Create a new file named cart.dart and add the following code to it:

   import 'package:mobx/mobx.dart';
   import 'item.dart';
   part 'cart.g.dart';
   class Cart = _Cart with _$Cart;
   abstract class _Cart with Store {
     List<Item> items = populateItems();
     @observable
     List<Item> cart = [];
     @action
     void addItemToCart(Item item) {
       var newCart = <Item>[];
       newCart.addAll(cart);
       newCart.add(item);
     ...