Add conceptual command pattern

CHANGELOG.md

@@ -1,5 +1,8 @@
+## 0.35.0
+- Add conceptual command pattern.
+
 ## 0.34.0
-- Add conceptual single pattern.
+- Add conceptual singleton pattern.
 
 ## 0.33.0
 - Add conceptual builder pattern.

README.md

@@ -11,7 +11,7 @@ It contains **Dart** examples for all classic **GoF** design patterns.
     - [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** - [[Text Editor](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/command/text_editor)] 
+    - [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)]
     - [ ] **Iterator**
     - [x] **Mediator** - [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/mediator/conceptual)]

patterns/command/conceptul/README.md

@@ -0,0 +1,47 @@
+# Command Pattern
+Command is a behavioral design pattern that turns a request into a stand-alone object that contains
+all information about the request.
+
+Tutorial: [here](https://refactoring.guru/design-patterns/command).
+
+## Diagram:
+![image](https://user-images.githubusercontent.com/8049534/183062798-c2e9207d-850c-47b6-bbba-3d669299d69f.png)
+
+## Client dode:
+```dart
+void main() {
+  final mutStr = MutStr();
+
+  final input1 = AddTextCommand('One', mutStr);
+  final input2 = AddTextCommand('Three', mutStr);
+  final input3 = InsertTextCommand(' Two ', mutStr, pos: 2);
+
+  input1.execute();
+  print('text = $mutStr'); // mutStr = "One"
+
+  input2.execute();
+  print('text = $mutStr'); // mutStr = "OneThree"
+
+  input3.execute();
+  print('text = $mutStr'); // mutStr = "One Two Three"
+
+  input3.undo();
+  print('text = $mutStr'); // mutStr = "OneThree"
+
+  input2.undo();
+  print('text = $mutStr'); // mutStr = "One "
+
+  input1.undo();
+  print('text = $mutStr'); // mutStr = ""
+}
+```
+
+### Output:
+```
+text = One
+text = OneThree
+text = One Two Three
+text = OneThree
+text = One
+text = 
+```

patterns/command/conceptul/command/add_text_command.dart

@@ -0,0 +1,26 @@
+import '../pattern/command.dart';
+import '../mut_str/mut_str.dart';
+
+class AddTextCommand implements Command {
+  final String addedText;
+  final MutStr mutStr;
+
+  AddTextCommand(this.addedText, this.mutStr);
+
+  @override
+  void execute() {
+    additionPosition = mutStr.len;
+    mutStr.push(addedText);
+  }
+
+  @override
+  void undo() {
+    if (additionPosition == null) {
+      return;
+    }
+
+    mutStr.delete(additionPosition!, additionPosition! + addedText.length);
+  }
+
+  int? additionPosition;
+}

patterns/command/conceptul/command/insert_text_command.dart

@@ -0,0 +1,27 @@
+import '../pattern/command.dart';
+import '../mut_str/mut_str.dart';
+
+class InsertTextCommand extends Command {
+  final int pos;
+  final String insertText;
+  final MutStr mutStr;
+
+  InsertTextCommand(this.insertText, this.mutStr, {required this.pos});
+
+  @override
+  void execute() {
+    _isNotExecute = false;
+    mutStr.insert(pos + 1, insertText);
+  }
+
+  @override
+  void undo() {
+    if (_isNotExecute) {
+      return;
+    }
+
+    mutStr.delete(pos + 1, insertText.length - 1);
+  }
+
+  bool _isNotExecute = true;
+}

patterns/command/conceptul/main.dart

@@ -0,0 +1,29 @@
+import 'mut_str/mut_str.dart';
+import 'command/add_text_command.dart';
+import 'command/insert_text_command.dart';
+
+void main() {
+  final mutStr = MutStr();
+
+  final input1 = AddTextCommand('One', mutStr);
+  final input2 = AddTextCommand('Three', mutStr);
+  final input3 = InsertTextCommand(' Two ', mutStr, pos: 2);
+
+  input1.execute();
+  print('text = $mutStr'); // mutStr = "One"
+
+  input2.execute();
+  print('text = $mutStr'); // mutStr = "OneThree"
+
+  input3.execute();
+  print('text = $mutStr'); // mutStr = "One Two Three"
+
+  input3.undo();
+  print('text = $mutStr'); // mutStr = "OneThree"
+
+  input2.undo();
+  print('text = $mutStr'); // mutStr = "One "
+
+  input1.undo();
+  print('text = $mutStr'); // mutStr = ""
+}

patterns/command/conceptul/mut_str/mut_str.dart

@@ -0,0 +1,22 @@
+class MutStr {
+  void push(String str) {
+    _buff.addAll(str.split(''));
+  }
+
+  void insert(int pos, String str) {
+    _buff.insert(pos, str);
+  }
+
+  void delete(int startPos, int len) {
+    _buff.removeRange(startPos, len);
+  }
+
+  int get len => _buff.length;
+
+  @override
+  String toString() {
+    return _buff.join('');
+  }
+
+  final _buff = <String>[];
+}

patterns/command/conceptul/pattern/command.dart

@@ -0,0 +1,4 @@
+abstract class Command {
+  void execute();
+  void undo();
+}

pubspec.yaml

@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.34.0
+version: 0.35.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue