Connect CartButton

lib/screens/product_list/cart_button.dart

@@ -1,17 +1,24 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_mobx/flutter_mobx.dart';
 import 'package:thesis_shop/benchmark_counter.dart';
 import 'package:thesis_shop/route_key.dart';
+import 'package:thesis_shop/stores/store_injector.dart';
 
 class CartButton extends StatelessWidget {
   const CartButton() : super(key: const Key('cart_button'));
 
   @override
   Widget build(BuildContext context) {
-    BenchmarkCounters.cartButton++;
-    return ElevatedButton.icon(
-      onPressed: () => Navigator.of(context).pushRouteKey(RouteKey.cart),
-      icon: const Icon(Icons.shopping_basket),
-      label: const Text('Warenkorb (3 Produkte)'),
+    final cartStore = StoreInjector.of(context).cartStore;
+    return Observer(
+      builder: (context) {
+        BenchmarkCounters.cartButton++;
+        return ElevatedButton.icon(
+          onPressed: () => Navigator.of(context).pushRouteKey(RouteKey.cart),
+          icon: const Icon(Icons.shopping_basket),
+          label: Text('Warenkorb (${cartStore.numberOfItems} Produkte)'),
+        );
+      },
     );
   }
 }

lib/stores/cart_store.dart

@@ -29,6 +29,9 @@ abstract class _CartStore with Store {
     return ObservableList.of(items);
   }
 
+  @computed
+  int get numberOfItems => cart.length;
+
   @action
   void _changeAmountOfProduct(Product product, int amount) {
     final oldValue = _productQuantities.putIfAbsent(product.title, () => 0);

lib/stores/cart_store.g.dart

@@ -16,6 +16,13 @@ mixin _$CartStore on _CartStore, Store {
       (_$cartComputed ??= Computed<ObservableList<CartItem>>(() => super.cart,
               name: '_CartStore.cart'))
           .value;
+  Computed<int>? _$numberOfItemsComputed;
+
+  @override
+  int get numberOfItems =>
+      (_$numberOfItemsComputed ??= Computed<int>(() => super.numberOfItems,
+              name: '_CartStore.numberOfItems'))
+          .value;
 
   final _$_productQuantitiesAtom = Atom(name: '_CartStore._productQuantities');
 
@@ -48,7 +55,8 @@ mixin _$CartStore on _CartStore, Store {
   @override
   String toString() {
     return '''
-cart: ${cart}
+cart: ${cart},
+numberOfItems: ${numberOfItems}
     ''';
   }
 }