fix inheritance

.gitignore

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+.dart_tool/
+.idea/
+build/
+windows/
+
+.packages
+pubspec.lock

CHANGELOG.md

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+## 0.38.0
+- Add conceptual facade pattern.
+
+## 0.37.0
+- Add iterator pattern: Word Iterator.
+
+## 0.36.0
+- Add iterator pattern: Github Commit.
+
+## 0.35.0
+- Add conceptual command pattern.
+
+## 0.34.0
+- Add conceptual singleton pattern.
+
+## 0.33.0
+- Add conceptual builder pattern.
+
+## 0.32.0
+- Add conceptual interpreter pattern.
+
+## 0.31.0
+- Add conceptual proxy pattern.
+
+## 0.30.0
+- Add strategy pattern: View Strategy.
+
+## 0.29.0
+- Add conceptual visitor pattern.
+
+## 0.28.0
+- Add conceptual flyweight pattern.
+
+## 0.27.0
+- Add template method pattern: Data Miner.
+
+## 0.26.0
+- Add conceptual mediator pattern.
+
+## 0.25.0
+- Add conceptual state pattern: Three State.
+
+## 0.24.1
+- Add flutter icon to project links.
+
+## 0.24.0
+- Add state pattern: State Manipulator.
+
+## 0.23.14
+- Replace web renderer html to canvakit (deploy_flutter_demo.dart).
+
+## 0.23.13
+- Update demos splash screen logo (Ukraine).
+
+## 0.23.12
+- Add properties bar to "Tool Panel Factory".
+
+## 0.23.0
+- Add "Tool Panel Factory" flutter example
+
+## 0.22.0
+- Add visitor pattern: "Shape Xml Export".
+
+## 0.21.0
+- Add strategy pattern: "Reservation cargo spaces".
+
+## 0.20.0
+- Add "Conceptual Dialog Factory" example.
+
+## 0.19.0
+- Add "Conceptual Gui Factory" example.
+
+## 0.18.0
+- Add Memento Editor.
+
+## 0.17.16 - refactoring
+- Simplifying the ternary construction.
+- Remove multiline comment from main README.
+- Replace repository urls to relative.
+- Fix relative urls.
+- Fix name on diagram "Builder", rename JsonFormat to JsonConverter.
+- Select pattern "Command" at the diagram.
+- Add client code to "Bridge" pattern.
+- Fix url position & add example name to ProductsAndBoxes example.
+- Add example name to Decorator pattern.
+- Format app_observer.dart.
+- Connect Application to events on the AppObserver diagram.
+- Split into separate files the "Memento" project.
+- Remover unnecessary import.
+- Move hash generator to application.
+- Update SubscriberWidget diagram.
+- Fix url position in FlutterAdapter README.md.
+
+## 0.17.0
+Add "Adapter" pattern: adapt a non-reactive classic type application for Flutter.
+
+## 0.16.5
+Add deploy_flutter_demos script.
+
+## 0.16.0
+- Add complex example of an Observer pattern, connected to a Flutter application.
+- Add new branch "web-demos" for online examples.
+
+## 0.15.0
+- Add second "Observer" example. This example was created to be used in a more complex example.
+
+## 0.14.0
+- Add "Memento" conceptual pattern
+
+## 0.13.0
+- Add "Observer" pattern from official book, rewritten from Java example
+
+## 0.12.19
+- Refactoring: reformatting and minor changes
+
+## 0.12.5
+- Put "Shapes" prototype pattern to "Shapes" folder
+- The list of patterns has been updated. Added links to projects
+
+## 0.12.0
+- Add "Command" pattern from official book, rewritten from Java example
+
+## 0.11.0
+- Add "Chain of Responsibility" pattern from official book, rewritten from Java example
+
+## 0.10.0
+- Add composite template from official book, rewritten from Java example
+
+## 0.9.0
+- Add decorator pattern. Translate from official book java example
+
+## 0.8.5
+- Add composite pattern "products_and_boxes"
+- Created a Canvas helper tool for visual presentation of patterns
+
+## 0.7.8
+- Update diagram for text_graphics, clock, remote_control, color_text_format
+- Code match with diagram in clock
+
+## 0.7.0
+- Add bridge pattern. Clock example
+
+## 0.6.5
+- Add bridge pattern. Device remote control
+
+## 0.5.5
+- Add example "graphics engine" and "square round conflict"  for adapter patter
+- Add description to prototype pattern
+- Fix class diagram for text graph
+- Add description Builder pattern, text formats
+- Add description to car builder pattern
+
+## 0.3.0
+- Add an example graphics engine for the adapter pattern
+
+## 0.2.0
+- Add the Builder pattern using file format converters as an example
+
+## 0.1.0
+- Add pattern Prototype  
+
+## 0.0.1
+
+- Initial project structure
+- Add README

CONTRIBUTING.md

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+## Contributor's Guide
+We appreciate any help, whether it's a simple fix of a typo or a whole new example. 
+Just [make a fork](https://help.github.com/articles/fork-a-repo/), 
+do your change and submit a [pull request](https://help.github.com/articles/creating-a-pull-request-from-a-fork/).
+
+### Step-by-step instruction
+1. Just make a fork.
+2. Clone the forked repository to your local machine.
+3. Create a new branch and name it, for example: fix-issue-32.
+4. Make changes.
+5. Create commits and push them to your forked Github repository.
+6. Submit a pull request to the master branch.
+7. Wait for review.
+
+### Style guide
+Here's a style guide which might help you to keep your changes consistent with our code:
+
+1. All code should meet the [Effective Dart: Style](https://dart.dev/guides/language/effective-dart/style).
+
+2. Use [Dart Format](https://dart.dev/tools/dart-format) or auto format shortcut `Ctrl + Alt + L` in your ide. 
+
+3. Try to hard wrap the code at 80th's character. It helps to list the code on the website without scrollbars.
+
+4. File names should match following convention: `some_class_name.dart`
+
+5. Comments may or may not have language tags in them, such as this:
+    ```dart
+        // EN: All products families have the same varieties (MacOS/Windows).
+        // This is a MacOS variant of a button.
+
+        // RU: Все семейства продуктов имеют одни и те же вариации (MacOS/Windows).
+        // Это вариант кнопки под MacOS.
+    ```
+    Don't be scared and ignore the non-English part of such comments. If you want to change 
+    something in a comment like this, then do it. Even if you do it wrong, we'll tell you how 
+    to fix it during the Pull Request.
+
+
+### Build Flutter examples
+```batch
+cd root directory
+flutter build web -t bin\main.dart
+```
+
+### Deploy flutter demos
+1. Fork this repo: `https://github.com/RefactoringGuru/design-patterns-dart`
+2. Apply your changes.
+3. Run the script `dart bin\deploy_flutter_demos.dart`.
+This script will build a web platform flutter app and push the changes to your **web-demos** branch on github.
+4. You can now make a pull request on the **web-demos** branch.
+5. Once approved for the merge, the web app will be available at https://refactoringguru.github.io/design-patterns-dart .

README.md

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+# Design Patterns in Dart
+This repository is part of the [**Refactoring.Guru**](https://refactoring.guru/design-patterns) project.
+It contains **Dart** examples for all classic **GoF** design patterns.
+
+# Implementation checklist:
+- [ ] **Creation**
+    - [x] **Abstract Factory** [[Conceptual Gui Factory](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/abstract_factory/conceptual_gui_factory)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) Tool Panel Factory](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/abstract_factory/tool_panel_factory)]
+    - [x] **Builder** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/builder/conceptual)] [[Color Text Format](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/builder/color_text_format)]
+    - [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)] 
+    - [x] **Singleton** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/singleton/conceptual)]
+- [ ]  **Behavioral**
+    - [x] **Chain of Responsibility** - [[Server Middleware](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/chain_of_responsibility/server_middleware)]
+    - [x] **Command** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/command/conceptual)] [[Text Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/command/text_editor)] 
+    - [x] **Interpreter**  - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/interpreter/conceptual)]
+    - [x] **Iterator** - [[Word Iterator](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/iterator/word_iterator)] [[Github Commit](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/iterator/github_commit)]
+    - [x] **Mediator** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/mediator/conceptual)]
+    - [x] **Memento** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/memento/conceptual)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) Memento Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/memento/memento_editor)] 
+    - [x] **Observer** - [[Open-Close Editor Events](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/observer/open_close_editor_events)] [[AppObserver](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/observer/app_observer)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) Subscriber Flutter Widget](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/observer/subscriber_flutter_widget)]
+    - [x] **State** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/state/three_state)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) State Manipulator](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/state/manipulator_state)]
+    - [x] **Template Method** - [[Data Miner](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/template_method/data_miner)] 
+    - [X] **Visitor** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/visitor/conceptual)] [[Shape XML Exporter](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/visitor/shapes_exporter)]
+    - [X] **Strategy** [[View Strategy](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/strategy/view_strategy)] [[Reservation Cargo Spaces](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/strategy/reservation_cargo_spaces)]
+- [ ] **Structural**
+    - [x] **Adapter** - [[Text Graphics](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/adapter/text_graphics)] [[Square Round conflict](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/adapter/square_round_conflict)] [[![16x16](https://user-images.githubusercontent.com/8049534/171852337-57db0faf-1f5e-489a-a79a-22ed4f47b4ed.png) Flutter Adapter](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/adapter/flutter_adapter)] 
+    - [x] **Bridge** - [[Remote Device Control](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/bridge/devices_remote_control)] [[Clock](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/bridge/clock)] 
+    - [x] **Composite** - [[Image Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/composite/image_editor)] [[Products and Boxes](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/composite/products_and_boxes)] 
+    - [x] **Decorator** - [[Data Source Decoder](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/decorator/data_source_decoder)]
+    - [x] **Facade** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/facade/conceptual)]
+    - [x] **Flyweight** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/flyweight/conceptual)]
+    - [x] **Proxy** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/proxy/conceptual)]
+
+## Requirements
+The examples were written in **Dart 2.17**.
+Some complex examples require **Flutter 3.0.0**.
+
+## Contributor's Guide
+We appreciate any help, whether it's a simple fix of a typo or a whole new example. 
+Just [make a fork](https://help.github.com/articles/fork-a-repo/), 
+do your change and submit a [pull request](https://help.github.com/articles/creating-a-pull-request-from-a-fork/).
+
+### Step-by-step instruction
+1. Just make a fork.
+2. Clone the forked repository to your local machine.
+3. Create a new branch and name it, for example: fix-issue-32.
+4. Make changes.
+5. Create commits and push them to your forked Github repository.
+6. Submit a pull request to the master branch.
+7. Wait for review.
+
+### Style guide
+Here's a style guide which might help you to keep your changes consistent with our code:
+
+1. All code should meet the [Effective Dart: Style](https://dart.dev/guides/language/effective-dart/style).
+
+2. Use [Dart Format](https://dart.dev/tools/dart-format) or auto format shortcut `Ctrl + Alt + L` in your ide. 
+
+3. Try to hard wrap the code at 80th's character. It helps to list the code on the website without scrollbars.
+
+4. File names should match following convention: `some_class_name.dart`
+
+5. Comments may or may not have language tags in them, such as this:
+    ```dart
+        // EN: All products families have the same varieties (MacOS/Windows).
+        // This is a MacOS variant of a button.
+
+        // RU: Все семейства продуктов имеют одни и те же вариации (MacOS/Windows).
+        // Это вариант кнопки под MacOS.
+    ```
+    Don't be scared and ignore the non-English part of such comments. If you want to change 
+    something in a comment like this, then do it. Even if you do it wrong, we'll tell you how 
+    to fix it during the Pull Request.
+
+
+### Build Flutter examples
+```batch
+cd root directory
+flutter build web -t bin\main.dart
+```
+
+### Deploy flutter demos
+1. Fork this repo: `https://github.com/RefactoringGuru/design-patterns-dart`
+2. Apply your changes.
+3. Run the script `dart bin\deploy_flutter_demos.dart`.
+This script will build a web platform flutter app and push the changes to your **web-demos** branch on github.
+4. You can now make a pull request on the **web-demos** branch.
+5. Once approved for the merge, the web app will be available at https://refactoringguru.github.io/design-patterns-dart .
+
+## License
+This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
+
+<a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-nc-nd/4.0/80x15.png" /></a>
+
+
+## Credits
+Authors: Alexander Shvets ([@neochief](https://github.com/neochief)), ilopX ([@ilopX](https://github.com/ilopX))

analysis_options.yaml

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+# This file configures the static analysis results for your project (errors,
+# warnings, and lints).
+#
+# This enables the 'recommended' set of lints from `package:lints`.
+# This set helps identify many issues that may lead to problems when running
+# or consuming Dart code, and enforces writing Dart using a single, idiomatic
+# style and format.
+#
+# If you want a smaller set of lints you can change this to specify
+# 'package:lints/core.yaml'. These are just the most critical lints
+# (the recommended set includes the core lints).
+# The core lints are also what is used by pub.dev for scoring packages.
+
+include: package:lints/recommended.yaml
+
+# Uncomment the following section to specify additional rules.
+
+linter:
+  rules:
+    library_private_types_in_public_api: false
+# analyzer:
+#   exclude:
+#     - path/to/excluded/files/**
+
+# For more information about the core and recommended set of lints, see
+# https://dart.dev/go/core-lints
+
+# For additional information about configuring this file, see
+# https://dart.dev/guides/language/analysis-options