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Merged
merged 2 commits into from
Jan 31, 2020
Merged

Follow best practice of ProxyProvider updating #298

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fc251e2
Upgrade to pkg:provider 4.0
filiph Jan 31, 2020
6c2435f
Follow best practice of ProxyProvider updating
filiph Jan 31, 2020
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8 changes: 5 additions & 3 deletions provider_shopper/lib/main.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -27,9 +27,11 @@ class MyApp extends StatelessWidget {
// of ChangeNotifierProvider. Moreover, CartModel depends
// on CatalogModel, so a ProxyProvider is needed.
ChangeNotifierProxyProvider<CatalogModel, CartModel>(
create: (context) => CartModel.empty(),
update: (context, catalog, previousCart) =>
CartModel(catalog, previousCart),
create: (context) => CartModel(),
update: (context, catalog, cart) {
cart.catalog = catalog;
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Nit but I'd use the .. operator instead of making a block

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To offer a counterpoint, in a sample that's aimed at beginners (like this one), we sometimes stretch out the syntax to maximize readability for new folks.

Entirely your call which way to go, though, Filip.

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@filiph filiph Jan 31, 2020 •
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Yes, I had the cascade operator there at first but went with the more verbose syntax for the reason @RedBrogdon mentions. We're not teaching Dart niceties here, so I go with as "vanilla" syntax as possible, so as to decrease cognitive load on the beginner user.

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@filiph @RedBrogdon Thanks a ton, As a beginner user it's very hard to understand these kind of syntax ..
vanilla syntax rocks:)

return cart;
},
),
],
child: MaterialApp(
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34 changes: 17 additions & 17 deletions provider_shopper/lib/models/cart.dart
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Expand Up @@ -6,25 +6,25 @@ import 'package:flutter/foundation.dart';
import 'package:provider_shopper/models/catalog.dart';

class CartModel extends ChangeNotifier {
/// The current catalog. Used to construct items from numeric ids.
final CatalogModel _catalog;
/// The private field backing [catalog].
CatalogModel _catalog;

/// Internal, private state of the cart. Stores the ids of each item.
final List<int> _itemIds;

/// Construct a CartModel instance that is backed by a [CatalogModel] and
/// an optional previous state of the cart.
///
/// If [previous] is not `null`, its items are copied to the newly
/// constructed instance.
CartModel(this._catalog, CartModel previous)
: assert(_catalog != null),
_itemIds = previous?._itemIds ?? [];

/// An empty cart with no Catalog.
CartModel.empty()
: _catalog = null,
_itemIds = [];
final List<int> _itemIds = [];

/// The current catalog. Used to construct items from numeric ids.
CatalogModel get catalog => _catalog;

set catalog(CatalogModel newCatalog) {
assert(newCatalog != null);
assert(_itemIds.every((id) => newCatalog.getById(id) != null),
'The catalog $newCatalog does not have one of $_itemIds in it.');
_catalog = newCatalog;
// Notify listeners, in case the new catalog provides information
// different from the previous one. For example, availability of an item
// might have changed.
notifyListeners();
}

/// List of items in the cart.
List<Item> get items => _itemIds.map((id) => _catalog.getById(id)).toList();
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10 changes: 9 additions & 1 deletion provider_shopper/pubspec.lock
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Expand Up @@ -88,6 +88,13 @@ packages:
url: "https://pub.dartlang.org"
source: hosted
version: "1.1.8"
nested:
dependency: transitive
description:
name: nested
url: "https://pub.dartlang.org"
source: hosted
version: "0.0.4"
path:
dependency: transitive
description:
Expand Down Expand Up @@ -115,7 +122,7 @@ packages:
name: provider
url: "https://pub.dartlang.org"
source: hosted
version: "3.2.0"
version: "4.0.2"
quiver:
dependency: transitive
description:
Expand Down Expand Up @@ -193,3 +200,4 @@ packages:
version: "3.5.0"
sdks:
dart: ">=2.5.0 <3.0.0"
flutter: ">=1.12.1"
2 changes: 1 addition & 1 deletion provider_shopper/pubspec.yaml
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Expand Up @@ -11,7 +11,7 @@ dependencies:
sdk: flutter

# Import the provider package.
provider: ^3.1.0
provider: ^4.0.2

dev_dependencies:
flutter_test:
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