Add factory method pattern.

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 0.20.0
+- Add "Conceptual Dialog Factory" example.
+
 ## 0.19.0
 - Add "Conceptual Gui Factory" example.
 

README.md

@@ -4,9 +4,9 @@ It contains **Dart** examples for all classic **GoF** design patterns.
 
 # Implementation checklist:
 - [ ] **Creation**
-    - [ ] **Abstract Factory** [[Conceptual Gui Factory](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/abstract_factory/conceptual_gui_factory)]
+    - [x] **Abstract Factory** [[Conceptual Gui Factory](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/abstract_factory/conceptual_gui_factory)]
     - [x] **Builder** - [[Color Text Format](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/builder/color_text_format)]
-    - [ ] **Factory Method**
+    - [x] **Factory Method** [[Conceptual Platform Dialog](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/factory_method/conceptual_platform_dialog)]
     - [x] **Prototype** - [[Shapes](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/prototype/shapes)] 
     - [ ] **Singleton**
 - [ ]  **Behavioral**

patterns/factory_method/concaptual_platform_dialog/README.md

@@ -0,0 +1,39 @@
+# Abstract Factory pattern
+Factory Method is a creational design pattern that provides an interface for creating objects in a 
+superclass, but allows subclasses to alter the type of objects that will be created.
+
+Tutorial: [here](https://refactoring.guru/design-patterns/factory-method).
+
+### About example.
+This the very conceptual example rewrite from original source code [java example](https://github.com/RefactoringGuru/design-patterns-java/tree/main/src/refactoring_guru/factory_method/example)
+
+### Diagram:
+![image](https://user-images.githubusercontent.com/8049534/166105090-a2b490fe-3e3e-44f1-a781-9777023020fb.png)
+
+### Client code:
+```dart
+late Dialog dialog;
+
+void main() {
+  configure();
+  runBusinessLogic();
+}
+
+void configure() {
+  if (Platform.isWindows) {
+    dialog = WindowsDialog();
+  } else {
+    dialog = HtmlDialog();
+  }
+}
+
+void runBusinessLogic() {
+  dialog.renderWindow();
+}
+```
+
+### Output:
+```
+Windows Button
+Click! Button says - "Hello World!"
+```

patterns/factory_method/concaptual_platform_dialog/buttons/button.dart

@@ -0,0 +1,10 @@
+/// EN: Common interface for all buttons.
+///
+/// RU: Общий интерфейс для всех продуктов.
+abstract class Button {
+  final void Function() onClick;
+
+  Button(this.onClick);
+
+  void render();
+}

patterns/factory_method/concaptual_platform_dialog/buttons/html_button.dart

@@ -0,0 +1,14 @@
+import 'button.dart';
+
+/// EN: HTML button implementation.
+///
+/// RU: Реализация HTML кнопок.
+class HtmlButton extends Button {
+  HtmlButton(void Function() onClick) : super(onClick);
+
+  @override
+  void render() {
+    print('<button>Test Button</button>');
+    onClick();
+  }
+}

patterns/factory_method/concaptual_platform_dialog/buttons/windows_button.dart

@@ -0,0 +1,14 @@
+import 'button.dart';
+
+/// EN: Windows button implementation.
+///
+/// RU: Реализация нативных кнопок операционной системы.
+class WindowsButton extends Button {
+  WindowsButton(void Function() onClick) : super(onClick);
+
+  @override
+  void render() {
+    print('Windows Button');
+    onClick();
+  }
+}

patterns/factory_method/concaptual_platform_dialog/dialogs_factory/dialog.dart

@@ -0,0 +1,21 @@
+import '../buttons/button.dart';
+
+abstract class Dialog {
+  void renderWindow() {
+    /// EN: ... other code ...
+    ///
+    /// RU: ... остальной код диалога ...
+
+    Button okButton = createButton(() {
+      print('Click! Button says - "Hello World!"');
+    });
+    okButton.render();
+  }
+
+  /// EN: Subclasses will override this method in order to create specific
+  /// button objects.
+  ///
+  /// RU: Подклассы будут переопределять этот метод, чтобы создавать конкретные
+  /// объекты продуктов, разные для каждой фабрики.
+  Button createButton(void Function() onClick);
+}

patterns/factory_method/concaptual_platform_dialog/dialogs_factory/html_dialog.dart

@@ -0,0 +1,11 @@
+import '../buttons/button.dart';
+import '../buttons/html_button.dart';
+import 'dialog.dart';
+
+/// EN: HTML Dialog will produce HTML buttons.
+///
+/// RU: HTML-диалог.
+class HtmlDialog extends Dialog {
+  @override
+  Button createButton(void Function() onClick) => HtmlButton(onClick);
+}

patterns/factory_method/concaptual_platform_dialog/dialogs_factory/windows_dialog.dart

@@ -0,0 +1,11 @@
+import '../buttons/button.dart';
+import '../buttons/windows_button.dart';
+import 'dialog.dart';
+
+/// EN: Windows Dialog will produce Windows buttons.
+///
+/// RU: Диалог на элементах операционной системы.
+class WindowsDialog extends Dialog {
+  @override
+  Button createButton(void Function() onClick) => WindowsButton(onClick);
+}

patterns/factory_method/concaptual_platform_dialog/main.dart

@@ -0,0 +1,36 @@
+import 'dart:io';
+
+import 'dialogs_factory/dialog.dart';
+import 'dialogs_factory/html_dialog.dart';
+import 'dialogs_factory/windows_dialog.dart';
+
+late Dialog dialog;
+
+void main() {
+  configure();
+  runBusinessLogic();
+}
+
+/// EN: The concrete factory is usually chosen depending on configuration or
+/// environment options.
+///
+/// RU: Приложение создаёт определённую фабрику в зависимости от конфигурации
+/// или окружения.
+void configure() {
+  if (Platform.isWindows) {
+    dialog = WindowsDialog();
+  } else {
+    dialog = HtmlDialog();
+  }
+}
+
+/// EN: All of the client code should work with factories and products
+/// through abstract interfaces. This way it does not care which factory it
+/// works with and what kind of product it returns.
+///
+/// RU: Весь остальной клиентский код работает с фабрикой и продуктами только
+/// через общий интерфейс, поэтому для него неважно какая фабрика была
+/// создана.
+void runBusinessLogic() {
+  dialog.renderWindow();
+}

pubspec.yaml

@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.19.0
+version: 0.20.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue