Merge pull request #1 from davidsdearaujo/main

[BuilderPlus] Include "buildWhen"
Flutterando · Jul 29, 2024 · 30abb55 · 30abb55
2 parents 7cfad0e + d931570
commit 30abb55
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diff --git a/README.md b/README.md
@@ -76,6 +76,23 @@ class CounterPage extends StatelessWidget {
 }
 ```
 
+**Para controlar com precisão quando a função `builder` é chamada, pode-se fornecer opcionalmente um `buildWhen`. O `buildWhen` recebe o estado anterior e o estado atual do `ValueNotifierPlus` e retorna um booleano. Se `buildWhen` retornar verdadeiro, `builder` será chamado com o `state` e o widget será reconstruído. Se `buildWhen` retornar falso, `builder` não será chamado com o `state` e nenhuma reconstrução ocorrerá.**
+
+```dart
+BuilderPlus<CounterNotifier, int>(
+  notifier: counterNotifier,
+  buildWhen: (previousState, state) {
+    // retorna true/false para determinar quando
+    // reconstruir o widget com o novo estado.
+    return state > previousState + 2;
+  },
+  builder: (context, state) {
+    return Text('Counter: $state');
+  },
+),
+```
+
+
 ### `ListenerPlus`
 
 O `ListenerPlus` é um widget que executa uma função sempre que o valor do `ValueNotifierPlus` muda, sem reconstruir a árvore de widgets. É similar ao `BlocListener` do pacote `flutter_bloc`.

diff --git a/lib/src/widgets/builder_plus.dart b/lib/src/widgets/builder_plus.dart
@@ -1,16 +1,20 @@
 import 'package:flutter/widgets.dart';
-import '../../value_notifier_plus.dart';
 
+import '../../value_notifier_plus.dart';
 import 'callbacks_plus.dart';
 
+typedef BuilderPlusWhen<T> = bool Function(T previous, T current);
+
 class BuilderPlus<N extends ValueNotifierPlus<S>, S> extends StatefulWidget {
   const BuilderPlus({
     Key? key,
     required this.builder,
     required this.notifier,
+    this.buildWhen,
   }) : super(key: key);
   final WidgetBuilderPlus<S> builder;
   final N notifier;
+  final BuilderPlusWhen? buildWhen;
 
   @override
   State<BuilderPlus<N, S>> createState() => _BuilderPlusState<N, S>();
@@ -40,9 +44,12 @@ class _BuilderPlusState<N extends ValueNotifierPlus<S>, S>
   }
 
   void _listener() {
-    setState(() {
-      state = notifier.state;
-    });
+    final buildWhen = widget.buildWhen;
+    if (buildWhen == null || buildWhen(state, notifier.state)) {
+      setState(() {
+        state = notifier.state;
+      });
+    }
   }
 
   @override

diff --git a/test/src/widgets/builder_plus_test.dart b/test/src/widgets/builder_plus_test.dart
@@ -1,25 +1,66 @@
-import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
 import 'package:value_notifier_plus/value_notifier_plus.dart';
 
 import '../../conter_notifier.dart';
 
 void main() {
-  testWidgets('BuilderPlus rebuilds when state changes', (tester) async {
-    final counterNotifier = CounterNotifier();
-
-    await tester.pumpWidget(
-      BuilderPlus<CounterNotifier, int>(
-        notifier: counterNotifier,
-        builder: (context, state) {
-          return Text('$state', textDirection: TextDirection.ltr);
-        },
-      ),
-    );
-
-    expect(find.text('0'), findsOneWidget);
-    counterNotifier.increment();
-    await tester.pump();
-    expect(find.text('1'), findsOneWidget);
+  group('BuilderPlus', () {
+    testWidgets('rebuilds when state changes', (tester) async {
+      final counterNotifier = CounterNotifier();
+
+      await tester.pumpWidget(
+        BuilderPlus<CounterNotifier, int>(
+          notifier: counterNotifier,
+          builder: (context, state) {
+            return Text('$state', textDirection: TextDirection.ltr);
+          },
+        ),
+      );
+
+      expect(find.text('0'), findsOneWidget);
+      counterNotifier.increment();
+      await tester.pump();
+      expect(find.text('1'), findsOneWidget);
+    });
+
+    testWidgets('do NOT rebuilds when "buildWhen" is not true', (tester) async {
+      final counterNotifier = CounterNotifier();
+
+      await tester.pumpWidget(
+        BuilderPlus<CounterNotifier, int>(
+          notifier: counterNotifier,
+          buildWhen: (previous, current) => current > previous + 2,
+          builder: (context, state) {
+            return Text('$state', textDirection: TextDirection.ltr);
+          },
+        ),
+      );
+
+      expect(find.text('0'), findsOneWidget);
+      counterNotifier.increment();
+      await tester.pump();
+      expect(find.text('0'), findsOneWidget);
+    });
+
+    testWidgets('rebuilds when "buildWhen" is true', (tester) async {
+      final counterNotifier = CounterNotifier();
+
+      await tester.pumpWidget(
+        BuilderPlus<CounterNotifier, int>(
+          notifier: counterNotifier,
+          builder: (context, state) {
+            return Text('$state', textDirection: TextDirection.ltr);
+          },
+        ),
+      );
+
+      expect(find.text('0'), findsOneWidget);
+      counterNotifier.increment();
+      counterNotifier.increment();
+      counterNotifier.increment();
+      await tester.pump();
+      expect(find.text('3'), findsOneWidget);
+    });
   });
 }