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c121b2d2a6
* Upgrade to pkg:provider 4.0 * Follow best practice of ProxyProvider updating The addresses feedback from https://github.com/flutter/samples/issues/245. Instead of constructing a new `CartModel`, we merely update the `catalog` field. We no longer need a fancy constructor, and `CartModel._catalog` cannot be final any more.
44 lines
1.5 KiB
Dart
44 lines
1.5 KiB
Dart
// Copyright 2019 The Flutter team. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/foundation.dart';
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import 'package:provider_shopper/models/catalog.dart';
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class CartModel extends ChangeNotifier {
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/// The private field backing [catalog].
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CatalogModel _catalog;
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/// Internal, private state of the cart. Stores the ids of each item.
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final List<int> _itemIds = [];
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/// The current catalog. Used to construct items from numeric ids.
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CatalogModel get catalog => _catalog;
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set catalog(CatalogModel newCatalog) {
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assert(newCatalog != null);
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assert(_itemIds.every((id) => newCatalog.getById(id) != null),
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'The catalog $newCatalog does not have one of $_itemIds in it.');
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_catalog = newCatalog;
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// Notify listeners, in case the new catalog provides information
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// different from the previous one. For example, availability of an item
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// might have changed.
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notifyListeners();
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}
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/// List of items in the cart.
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List<Item> get items => _itemIds.map((id) => _catalog.getById(id)).toList();
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/// The current total price of all items.
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int get totalPrice =>
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items.fold(0, (total, current) => total + current.price);
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/// Adds [item] to cart. This is the only way to modify the cart from outside.
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void add(Item item) {
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_itemIds.add(item.id);
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// This line tells [Model] that it should rebuild the widgets that
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// depend on it.
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notifyListeners();
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}
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}
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