Upgrade provider shopper (#521)

MAINTENANCE.md

@@ -17,6 +17,6 @@ match any new language/SDK features, etc.).
 | platform_design           | johnpryan          | 10/7/19        |
 | platform_view_swift       | redbrogdon         | 10/7/19        |
 | provider_counter          | filiph             | 8/13/20        |
-| provider_shopper          | redbrogdon         | 11/21/19       |
+| provider_shopper          | filiph             | 8/13/20        |
 | testing_app               |                    |                |
 | veggieseasons             | filiph             | 8/13/20        |

provider_shopper/ios/Runner.xcodeproj/project.pbxproj

@@ -9,11 +9,7 @@
 /* Begin PBXBuildFile section */
 		1498D2341E8E89220040F4C2 /* GeneratedPluginRegistrant.m in Sources */ = {isa = PBXBuildFile; fileRef = 1498D2331E8E89220040F4C2 /* GeneratedPluginRegistrant.m */; };
 		3B3967161E833CAA004F5970 /* AppFrameworkInfo.plist in Resources */ = {isa = PBXBuildFile; fileRef = 3B3967151E833CAA004F5970 /* AppFrameworkInfo.plist */; };
-		3B80C3941E831B6300D905FE /* App.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 3B80C3931E831B6300D905FE /* App.framework */; };
-		3B80C3951E831B6300D905FE /* App.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = 3B80C3931E831B6300D905FE /* App.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		74858FAF1ED2DC5600515810 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 74858FAE1ED2DC5600515810 /* AppDelegate.swift */; };
-		9705A1C61CF904A100538489 /* Flutter.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 9740EEBA1CF902C7004384FC /* Flutter.framework */; };
-		9705A1C71CF904A300538489 /* Flutter.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = 9740EEBA1CF902C7004384FC /* Flutter.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		97C146FC1CF9000F007C117D /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FA1CF9000F007C117D /* Main.storyboard */; };
 		97C146FE1CF9000F007C117D /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FD1CF9000F007C117D /* Assets.xcassets */; };
 		97C147011CF9000F007C117D /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FF1CF9000F007C117D /* LaunchScreen.storyboard */; };
@@ -26,8 +22,6 @@
 			dstPath = "";
 			dstSubfolderSpec = 10;
 			files = (
-				3B80C3951E831B6300D905FE /* App.framework in Embed Frameworks */,
-				9705A1C71CF904A300538489 /* Flutter.framework in Embed Frameworks */,
 			);
 			name = "Embed Frameworks";
 			runOnlyForDeploymentPostprocessing = 0;
@@ -38,13 +32,11 @@
 		1498D2321E8E86230040F4C2 /* GeneratedPluginRegistrant.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GeneratedPluginRegistrant.h; sourceTree = "<group>"; };
 		1498D2331E8E89220040F4C2 /* GeneratedPluginRegistrant.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GeneratedPluginRegistrant.m; sourceTree = "<group>"; };
 		3B3967151E833CAA004F5970 /* AppFrameworkInfo.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; name = AppFrameworkInfo.plist; path = Flutter/AppFrameworkInfo.plist; sourceTree = "<group>"; };
-		3B80C3931E831B6300D905FE /* App.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = App.framework; path = Flutter/App.framework; sourceTree = "<group>"; };
 		74858FAD1ED2DC5600515810 /* Runner-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "Runner-Bridging-Header.h"; sourceTree = "<group>"; };
 		74858FAE1ED2DC5600515810 /* AppDelegate.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		7AFA3C8E1D35360C0083082E /* Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = Release.xcconfig; path = Flutter/Release.xcconfig; sourceTree = "<group>"; };
 		9740EEB21CF90195004384FC /* Debug.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; name = Debug.xcconfig; path = Flutter/Debug.xcconfig; sourceTree = "<group>"; };
 		9740EEB31CF90195004384FC /* Generated.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; name = Generated.xcconfig; path = Flutter/Generated.xcconfig; sourceTree = "<group>"; };
-		9740EEBA1CF902C7004384FC /* Flutter.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Flutter.framework; path = Flutter/Flutter.framework; sourceTree = "<group>"; };
 		97C146EE1CF9000F007C117D /* Runner.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Runner.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		97C146FB1CF9000F007C117D /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.storyboard; name = Base; path = Base.lproj/Main.storyboard; sourceTree = "<group>"; };
 		97C146FD1CF9000F007C117D /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
@@ -57,8 +49,6 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				9705A1C61CF904A100538489 /* Flutter.framework in Frameworks */,
-				3B80C3941E831B6300D905FE /* App.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -68,9 +58,7 @@
 		9740EEB11CF90186004384FC /* Flutter */ = {
 			isa = PBXGroup;
 			children = (
-				3B80C3931E831B6300D905FE /* App.framework */,
 				3B3967151E833CAA004F5970 /* AppFrameworkInfo.plist */,
-				9740EEBA1CF902C7004384FC /* Flutter.framework */,
 				9740EEB21CF90195004384FC /* Debug.xcconfig */,
 				7AFA3C8E1D35360C0083082E /* Release.xcconfig */,
 				9740EEB31CF90195004384FC /* Generated.xcconfig */,
@@ -201,7 +189,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" thin";
+			shellScript = "/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" embed_and_thin";
 		};
 		9740EEB61CF901F6004384FC /* Run Script */ = {
 			isa = PBXShellScriptBuildPhase;

provider_shopper/lib/screens/cart.dart

@@ -37,7 +37,10 @@ class _CartList extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     var itemNameStyle = Theme.of(context).textTheme.headline6;
-    var cart = Provider.of<CartModel>(context);
+    // This gets the current state of CartModel and also tells Flutter
+    // to rebuild this widget when CartModel notifies listeners (in other words,
+    // when it changes).
+    var cart = context.watch<CartModel>();
 
     return ListView.builder(
       itemCount: cart.items.length,
@@ -64,6 +67,12 @@ class _CartTotal extends StatelessWidget {
         child: Row(
           mainAxisAlignment: MainAxisAlignment.center,
           children: [
+            // Another way to listen to a model's change is to include
+            // the Consumer widget. This widget will automatically listen
+            // to CartModel and rerun its builder on every change.
+            //
+            // The important thing is that it will not rebuild
+            // the rest of the widgets in this build method.
             Consumer<CartModel>(
                 builder: (context, cart, child) =>
                     Text('\$${cart.totalPrice}', style: hugeStyle)),

provider_shopper/lib/screens/catalog.dart

@@ -32,14 +32,30 @@ class _AddButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    var cart = Provider.of<CartModel>(context);
+    // The context.select() method will let you listen to changes to
+    // a *part* of a model. You define a function that "selects" (i.e. returns)
+    // the part you're interested in, and the provider package will not rebuild
+    // this widget unless that particular part of the model changes.
+    //
+    // This can lead to significant performance improvements.
+    var isInCart = context.select<CartModel, bool>(
+      // Here, we are only interested whether [item] is inside the cart.
+      (cart) => cart.items.contains(item),
+    );
 
     return FlatButton(
-      onPressed: cart.items.contains(item) ? null : () => cart.add(item),
+      onPressed: isInCart
+          ? null
+          : () {
+              // If the item is not in cart, we let the user add it.
+              // We are using context.read() here because the callback
+              // is executed whenever the user taps the the button. In other
+              // words, it is executed outside the build method.
+              var cart = context.read<CartModel>();
+              cart.add(item);
+            },
       splashColor: Theme.of(context).primaryColor,
-      child: cart.items.contains(item)
+      child: isInCart ? Icon(Icons.check, semanticLabel: 'ADDED') : Text('ADD'),
-          ? Icon(Icons.check, semanticLabel: 'ADDED')
-          : Text('ADD'),
     );
   }
 }
@@ -67,8 +83,11 @@ class _MyListItem extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    var catalog = Provider.of<CatalogModel>(context);
+    var item = context.select<CatalogModel, Item>(
-    var item = catalog.getByPosition(index);
+      // Here, we are only interested in the item at [index]. We don't care
+      // about any other change.
+      (catalog) => catalog.getByPosition(index),
+    );
     var textTheme = Theme.of(context).textTheme.headline6;
 
     return Padding(

provider_shopper/pubspec.lock

@@ -1,13 +1,27 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
+  archive:
+    dependency: transitive
+    description:
+      name: archive
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.13"
+  args:
+    dependency: transitive
+    description:
+      name: args
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.6.0"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.2"
+    version: "2.4.1"
   boolean_selector:
     dependency: transitive
     description:
@@ -15,13 +29,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.0"
-  characters:
-    dependency: transitive
-    description:
-      name: characters
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.0"
   charcode:
     dependency: transitive
     description:
@@ -29,27 +36,27 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.3"
-  clock:
-    dependency: transitive
-    description:
-      name: clock
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.0.1"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.13"
+    version: "1.14.12"
-  fake_async:
+  convert:
     dependency: transitive
     description:
-      name: fake_async
+      name: convert
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "2.1.1"
+  crypto:
+    dependency: transitive
+    description:
+      name: crypto
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.4"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -60,13 +67,20 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  image:
+    dependency: transitive
+    description:
+      name: image
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.12"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.8"
+    version: "0.12.6"
   meta:
     dependency: transitive
     description:
@@ -87,7 +101,7 @@ packages:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.6.4"
   pedantic:
     dependency: "direct dev"
     description:
@@ -95,13 +109,27 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.9.0"
+  petitparser:
+    dependency: transitive
+    description:
+      name: petitparser
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.4.0"
   provider:
     dependency: "direct main"
     description:
       name: provider
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.1.0"
+    version: "4.3.2"
+  quiver:
+    dependency: transitive
+    description:
+      name: quiver
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.3"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -120,7 +148,7 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.5"
+    version: "1.9.3"
   stream_channel:
     dependency: transitive
     description:
@@ -148,14 +176,14 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.17"
+    version: "0.2.15"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.1.6"
   vector_math:
     dependency: transitive
     description:
@@ -163,6 +191,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.8"
+  xml:
+    dependency: transitive
+    description:
+      name: xml
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "3.6.1"
 sdks:
-  dart: ">=2.9.0-14.0.dev <3.0.0"
+  dart: ">=2.7.0 <3.0.0"
-  flutter: ">=1.17.0"
+  flutter: ">=1.16.0"

provider_shopper/pubspec.yaml

@@ -11,7 +11,7 @@ dependencies:
     sdk: flutter
 
   # Import the provider package.
-  provider: ^4.0.2
+  provider: ^4.3.2
 
 dev_dependencies:
   flutter_test: