Merge pull request #66 from ilopX/add-conceptual-flyweight-pattern

Add conceptual flyweight pattern

Author: ilopX

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 0.28.0
+- Add conceptual flyweight pattern.
+
 ## 0.27.0
 - Add template method pattern: Data Miner.
 

README.md

@@ -27,7 +27,7 @@ It contains **Dart** examples for all classic **GoF** design patterns.
     - [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)]
     - [ ] **Facade**
-    - [ ] **Flyweight**
+    - [x] **Flyweight** [[Conceptual](https://github.com/RefactoringGuru/design-patterns-dart/tree/main/patterns/flyweight/conceptual)]
     - [ ] **Proxy**
 
 ## Requirements

patterns/flyweight/conceptual/README.md

@@ -0,0 +1,50 @@
+# Flyweight Pattern
+Flyweight is a structural design pattern that lets you fit more objects into the available amount of
+ RAM by sharing common parts of state between multiple objects instead of keeping all of the data in
+  each object.
+
+Tutorial: [here](https://refactoring.guru/design-patterns/flyweight).
+
+### Conceptual Diagram:
+![Flyweight Pattern Diagram](https://user-images.githubusercontent.com/8049534/174476638-007f3179-495f-499d-8f35-e33956d4890b.png)
+
+### Client code:
+```dart
+void main() {
+  final factory = FlyweightFactory();
+
+  final one = factory.create('one');
+  one.draw();
+
+  final ONE = factory.create('ONE');
+  ONE.draw();
+
+  final OnE = factory.create('OnE');
+  OnE.draw();
+
+  final two = factory.create('two');
+  two.draw();
+
+  final Two = factory.create('Two');
+  Two.draw();
+}
+```
+
+### Output:
+```
+Flyweight(
+	localParam: "one", shareParam: (61, "b", 0.19)
+)
+Flyweight(
+	localParam: "ONE", shareParam: (61, "b", 0.19)
+)
+Flyweight(
+	localParam: "OnE", shareParam: (61, "b", 0.19)
+)
+Flyweight(
+	localParam: "two", shareParam: (53, "e", 0.55)
+)
+Flyweight(
+	localParam: "Two", shareParam: (53, "e", 0.55)
+)
+```

patterns/flyweight/conceptual/main.dart

@@ -0,0 +1,22 @@
+// ignore_for_file: non_constant_identifier_names
+
+import 'pattern/flyweight_factory.dart';
+
+void main() {
+  final factory = FlyweightFactory();
+
+  final one = factory.create('one');
+  one.draw();
+
+  final ONE = factory.create('ONE');
+  ONE.draw();
+
+  final OnE = factory.create('OnE');
+  OnE.draw();
+
+  final two = factory.create('two');
+  two.draw();
+
+  final Two = factory.create('Two');
+  Two.draw();
+}

patterns/flyweight/conceptual/params/share_params.dart

@@ -0,0 +1,7 @@
+class ShareParams {
+  final int param1;
+  final String param2;
+  final double param3;
+
+  ShareParams(this.param1, this.param2, this.param3);
+}

patterns/flyweight/conceptual/pattern/flyweight.dart

@@ -0,0 +1,17 @@
+import '../params/share_params.dart';
+
+class Flyweight {
+  final String localParam;
+  final ShareParams shareParams;
+
+  Flyweight(this.localParam, this.shareParams);
+
+  void draw() {
+    print('Flyweight(');
+    print('\tlocalParam: "$localParam", shareParam: ('
+        '${shareParams.param1}, '
+        '"${shareParams.param2}", '
+        '${shareParams.param3})');
+    print(')');
+  }
+}

patterns/flyweight/conceptual/pattern/flyweight_factory.dart

@@ -0,0 +1,20 @@
+import 'flyweight.dart';
+import '../params/share_params.dart';
+import '../utils/fake_value.dart';
+
+class FlyweightFactory {
+  Flyweight create(String localParam) {
+    final shareParams = _shares.putIfAbsent(
+      localParam.toLowerCase(),
+      () => ShareParams(
+        fakeInt,
+        fakeString,
+        fakeDouble,
+      ),
+    );
+
+    return Flyweight(localParam, shareParams);
+  }
+
+  final _shares = <String, ShareParams>{};
+}

patterns/flyweight/conceptual/utils/fake_value.dart

@@ -0,0 +1,12 @@
+import 'dart:math';
+
+String str = 'abcdef';
+get fakeString {
+  final char = str[Random().nextInt(str.length - 1)];
+  str = str.replaceFirst(char, '');
+  return char;
+}
+
+get fakeInt => Random().nextInt(100);
+
+get fakeDouble => Random().nextInt(100) / 100;

pubspec.yaml

@@ -1,6 +1,6 @@
 name: design_patterns_dart
 description: Dart examples for all classic GoF design patterns.
-version: 0.27.0
+version: 0.28.0
 homepage: https://refactoring.guru/design-patterns
 repository: https://github.com/RefactoringGuru/design-patterns-dart
 issue_tracker: https://github.com/RefactoringGuru/design-patterns-dart/issue