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‎README.md

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# Dart Programming Language
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## OOP
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- <strong><a href="1_oop/README.md" target="_blank">What Is OOP ?!</a></strong>
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- <strong><a href="1_oop/" target="_blank">What Is OOP ?!</a></strong>
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## Design Patterns
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reusable solution to a commonly occurring problem within a given context in software design.
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- Concept of inheritance is used to compose interfaces and define ways to compose objects to obtain new functionalities.
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- <strong><a href="structural_design_pattern/Adapter/README.md" target="_blank">Adapter</a></strong>
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- <strong><a href="structural_design_pattern/Adapter/" target="_blank">Adapter</a></strong>
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- <strong><a href="structural_design_pattern/bridge/README.md" target="_blank">Bridge</a></strong>
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- <strong><a href="structural_design_pattern/bridge/" target="_blank">Bridge</a></strong>
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- <strong><a href="structural_design_pattern/facade/" target="_blank">Facade</a></strong>
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‎structural_design_pattern/facade/README.md

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# Facade Structural Design Pattern
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> hides the complexities of the system by a class that provide a simple interface to a complex subsystem which contains lots of moving parts.
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<center><table>
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<tr>
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<td><img src="assets/Facade_Design_Pattern_Class_Diagram_UML_wikipedia_2.png"></td>
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<td><img src="assets/Facade_Design_Pattern_Sequence_Diagram_UML_wikipeda.png"><td>
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<td><img src="assets/Example_of_Facade_design_pattern_in_UML.png"></td>
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</tr>
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</table></center>
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<center><img width=75% src="assets/facade-diagram.png"></center>
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## Sections
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- [Definitions](#Definitions)
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- [What Problem Facade Solve?](#What-Problem-Facade-Solve?)
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- [Examples](#Examples)
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- [file converter example ](#file-converter-example)
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- [Shape Marker](#Shape-Marker) Tutorial point Example
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- [Sources](#Sources)
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## **Definitions**
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<dl>
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<dt><b>tutorialspoint </b></dt>
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<dd>
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<li>is a structural pattern.</li>
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<li> this pattern adds an interface to existing system to hide its complexities.</li>
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<li> and provides an interface to the client using which the client can access the system.</li>
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</dd>
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<dt><b>refactoring.guru </b></dt>
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<dd>
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<li>a structural pattern</li>
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<li>provides a simplified interface to a library, a framework, or any other complex set of classes.</li>
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</dd>
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</dd>
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<dt><b>Wikipedia </b></dt>
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<dd>
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<li>a structural pattern</li>
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<li>provides a simplified interface to a library, a framework, or any other complex set of classes.</li>
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</br>
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<li>Facade describe how to solve recurring design problems</li>
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<li>to design flexible and reusable object-oriented software, that is, objects that are easier to implement, change, test, and reuse.</li>
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</dd>
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</dl>
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</br>
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## **What Problem Facade Solve?**
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- Imagine that you must make your code work with a broad set of objects that belong to a sophisticated library or framework.
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- Ordinarily, you’d need to initialize all of those objects, keep track of dependencies, execute methods in the correct order, and so on.
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> As a result, the business logic of your classes would become tightly coupled to the implementation details of 3rd-party classes, making it hard to comprehend and maintain.
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---
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### Solution
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- A facade is a `class` that provides a simple interface to a complex subsystem which contains lots of moving parts.
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- A facade might provide limited functionality in comparison to working with the subsystem directly.
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- However, it includes only those features that clients really care about.
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- Having a facade is handy when you need to integrate your app with a sophisticated library that has dozens of features, but you just need a tiny bit of its functionality.
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## **Examples**
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### file converter example
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- Example in dart: <a href="file converter example ="_blank">file converter example </a>
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- Example Source:
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- <a href="https://refactoring.guru/design-patterns/bridge" target="_blank" >https://refactoring.guru/design-patterns/bridge</a>
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- <a href="https://www.tutorialspoint.com/design_pattern/bridge_pattern.htm" target="_blank" >https://www.tutorialspoint.com/design_pattern/bridge_pattern.htm</a>
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### Shape Marker
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- source: <a href="https://www.tutorialspoint.com/design_pattern/facade_pattern.htm" target="_blank">tutorialspoint.com/design_pattern/facade_pattern</a>
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- Example in dart: <a href="shape_marker.dart" target="_blank">Shape Marker</a>
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## **Sources**
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- <a href="https://en.wikipedia.org/wiki/Facade_pattern" target="_blank"> wikipedia.org Facade_pattern</a>
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- <a href="https://refactoring.guru/design-patterns/facade" target="_blank"> refactoring.guru design-patterns facade</a>
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- <a href="https://www.tutorialspoint.com/design_pattern/facade_pattern.htm" target="_blank"> www.tutorialspoint.com facade_pattern </a>
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‎structural_design_pattern/facade/assets/Example_of_Facade_design_pattern_in_UML.png

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‎structural_design_pattern/facade/assets/Facade_Design_Pattern_Class_Diagram_UML_wikipedia_2.png

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‎structural_design_pattern/facade/assets/Facade_Design_Pattern_Sequence_Diagram_UML_wikipeda.png

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‎structural_design_pattern/facade/assets/facade-diagram.png

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‎structural_design_pattern/facade/file_converter/FileConverterFacade.dart

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import 'compress.dart';
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import 'converter.dart';
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import 'file_scanner.dart';
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import 'normalizer.dart';
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class FileConverterFacade {
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String _file;
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bool _isAudio = true;
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late IFileScanner _fileScanner;
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late INormalizer _normalizer;
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late IConverter _converter;
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late ICompress _fileCompress;
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FileConverterFacade(String filePath) : _file = filePath {
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_detectType();
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_load();
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}
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void _detectType() {
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String fileExtension = _file.split('.').last;
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if (["mp3", "aa", "aac"].contains(fileExtension)) {
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_fileScanner = MP3FileScanner(_file);
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_normalizer = AudioNormalizer();
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_converter = AudioConverter();
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_fileCompress = ZipCompress();
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} else {
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_fileScanner = MP4FileScanner(_file);
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_normalizer = VideoNormalizer();
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_converter = VideoConverter();
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_fileCompress = RarCompress();
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_isAudio = false;
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}
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}
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void _load() {
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if (_fileScanner.scan()) {
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_normalizer.normalize(_file);
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} else {
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// let this be an CorruptedFileException ;
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// but for now we will print just error
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print("error from file Scan");
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}
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}
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convert() {
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if (_isAudio) {
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_converter.convert(
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_file, AudioTypes.AUDIO_MP3.name, AudioTypes.AUDIO_AAC.name);
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} else {
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_converter.convert(
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_file, VideoTypes.AUDIO_MP4.name, VideoTypes.AUDIO_AVI.name);
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}
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_fileCompress.compress(_file);
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}
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}

‎structural_design_pattern/facade/file_converter/README.md

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# File Converter Example
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<img src ="file_converter.png" />
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<img src ="../assets/Facade_Design_Pattern_Sequence_Diagram_UML_wikipeda.png" />

‎structural_design_pattern/facade/file_converter/compress.dart

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abstract class ICompress {
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void compress(String fileName);
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}
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class RarCompress implements ICompress {
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@override
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void compress(String fileName) =>
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print("File has been compressed to a rar file\n");
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}
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class ZipCompress implements ICompress {
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@override
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void compress(String fileName) =>
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print("File has been compressed to a zip file\n");
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}

‎structural_design_pattern/facade/file_converter/converter.dart

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abstract class IConverter {
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void convert(String fileName, String fromType, String toType);
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}
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enum AudioTypes { AUDIO_MP3, AUDIO_AA, AUDIO_AAC }
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enum VideoTypes { AUDIO_MP4, AUDIO_AVI, AUDIO_FLV }
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class AudioConverter implements IConverter {
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void convert(String fileName, String fromType, String toType) => print(
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"I am converting audio file $fileName from $fromType to $toType \n");
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}
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class VideoConverter implements IConverter {
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void convert(String fileName, String fromType, String toType) =>
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print("I am converting the file $fileName from $fromType to $toType \n");
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}

‎structural_design_pattern/facade/file_converter/file_converter.drawio

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<mxfile host="app.diagrams.net" modified="2022-04-02T13:25:40.183Z" agent="5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.74 Safari/537.36 Edg/99.0.1150.55" etag="jHKP1zxxewkc5JKrZXjo" version="17.1.5" type="device"><diagram id="C5RBs43oDa-KdzZeNtuy" name="Page-1">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</diagram></mxfile>

‎structural_design_pattern/facade/file_converter/file_converter.png

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‎structural_design_pattern/facade/file_converter/file_scanner.dart

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import 'dart:math' as math;
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abstract class IFileScanner {
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String file;
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IFileScanner(String this.file);
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bool scan();
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}
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class MP3FileScanner extends IFileScanner {
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MP3FileScanner(String file) : super(file);
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@override
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bool scan() => math.Random().nextInt(10) > 5;
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}
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class MP4FileScanner extends IFileScanner {
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MP4FileScanner(String file) : super(file);
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// Do a lot of stuff here then return the file status
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@override
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bool scan() => math.Random().nextInt(10) > 5;
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}

‎structural_design_pattern/facade/file_converter/main.dart

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import 'FileConverterFacade.dart';
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void main(List<String> args) {
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FileConverterFacade fileConverterFacade = FileConverterFacade('wild.mp3');
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fileConverterFacade.convert();
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}

‎structural_design_pattern/facade/file_converter/normalizer.dart

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abstract class INormalizer {
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void normalize(String fileName);
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}
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class AudioNormalizer implements INormalizer {
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@override
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void normalize(String fileName) => print(
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"I am normalizing the file $fileName due to some data corruption\n");
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}
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class VideoNormalizer implements INormalizer {
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@override
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void normalize(String fileName) => print(
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"I am normalizing the video $fileName due to some data corruption\n");
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}

‎structural_design_pattern/facade/shape_maker.dart

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//!
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//! BAD EXAMPLE FROM TUTORIAL POINT
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//! Source:: https://www.tutorialspoint.com/design_pattern/facade_pattern.htm
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// ShapeMaker class uses the concrete classes to delegate user calls to these classes.
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// main, our demo class, will use ShapeMaker class to show the results.
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// Step 1
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// Create an interface.
10+
abstract class IShape {
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void draw();
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}
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// Step 2
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// Create concrete classes implementing the same interface.
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class Rectangle implements IShape {
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@override
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void draw() => print("Rectangle::draw()");
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}
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class Square implements IShape {
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@override
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void draw() => print("Square::draw()");
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}
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class Circle implements IShape {
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@override
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void draw() => print("Circle::draw()");
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}
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31+
// Step 3
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// Create a facade class.
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class ShapeMaker {
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IShape _circle;
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IShape _rectangle;
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IShape _square;
37+
38+
ShapeMaker()
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: _circle = Circle(),
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_rectangle = Rectangle(),
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_square = Square();
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void drawCircle() => _circle.draw();
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void drawRectangle() => _rectangle.draw();
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void drawSquare() => _square.draw();
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}
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// Step 4
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// Use the facade to draw various types of shapes.
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void main() {
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ShapeMaker shapeMaker = ShapeMaker();
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shapeMaker.drawCircle();
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shapeMaker.drawRectangle();
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shapeMaker.drawSquare();
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}
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// Step 5
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// output.
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// Circle::draw()
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// Rectangle::draw()
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// Square::draw()

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