shape factory baby

lib/main.dart

@@ -20,6 +20,32 @@ class MyApp extends StatelessWidget {
   }
 }
 
+abstract class ShapeFactory {
+  Widget build(Size size, Color color);
+}
+
+class SquareFactory extends ShapeFactory {
+  @override
+  Widget build(Size size, Color color) {
+    return SizedBox.fromSize(
+      size: size,
+      child: Container(color: color),
+    );
+  }
+}
+
+class CircleFactory extends ShapeFactory {
+  @override
+  Widget build(Size size, Color color) {
+    return SizedBox.fromSize(
+      size: size,
+      child: Container(
+        decoration: BoxDecoration(shape: BoxShape.circle, color: color),
+      ),
+    );
+  }
+}
+
 class MyHomePage extends StatefulWidget {
   const MyHomePage({super.key});
 
@@ -28,6 +54,18 @@ class MyHomePage extends StatefulWidget {
 }
 
 class _MyHomePageState extends State<MyHomePage> {
+  final List<ShapeFactory> shapeFactories = [CircleFactory(), SquareFactory()];
+  int factoryIndex = 0;
+  ShapeFactory get factory => shapeFactories[factoryIndex];
+
+  void swapFactories() {
+    if (factoryIndex == 0) {
+      setState(() => factoryIndex = 1);
+      return;
+    }
+    setState(() => factoryIndex = 0);
+  }
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -39,12 +77,17 @@ class _MyHomePageState extends State<MyHomePage> {
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
-            const Text(
-              'You have pushed the button this many times:',
-            ),
-            Text(
-              'some text',
-              style: Theme.of(context).textTheme.headlineMedium,
+            const Text('Abstract Factories!!'),
+            Text('Using ${shapeFactories[factoryIndex].runtimeType.toString()}'),
+            ...List.generate(
+                3,
+                (index) => factory.build(
+                      Size(20.0 * (index + 1), 30.0 * (index + 1)),
+                      [Colors.red, Colors.green, Colors.blue][index],
+                    )),
+            ElevatedButton(
+              onPressed: () => swapFactories(),
+              child: const Text('Swap Factories'),
             ),
           ],
         ),