Add Composite (ES5 + ES6 + CoffeeScript)

Author: Badacadabra

doc/GoF/Structural/Composite/Composite.dia

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+# Synopsis
+
+My little brother's room is generally a big mess, but recently my mother bought him some funny toy boxes of different sizes (like a 3D puzzle) so he can put his toys in it.
+
+# Problem
+
+Here a toy box is, to some extent, a toy in itself that can contain other toys. These toys can be simple ones like, for instance, balls. But they can be complex ones too, like smaller toy boxes which also may contain other balls and/or even smaller toy boxes, etc. This situation is not easy to describe through code...
+
+# Solution
+
+A good idea is to consider a group of toys like a simple toy. So a toy box full of toys is just a toy after all!
+
+The Composite design pattern is useful in this kind of situation. To implement this one, we need:
+
+  * An abstract representation of a toy (abstract class or interface)
+  * Concrete toys, especially a simple one (ball) and a complex one (toy box)
+  * Methods for the complex toy to manage (simple and complex) toys inside of it

doc/GoF/Structural/Composite/Composite.png

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+"use strict"
+
+# ==============================
+# ABSTRACT COMPONENT
+# ==============================
+
+class Toy
+    constructor: ->
+        throw new Error "You cannot instantiate an abstract class!" if @constructor is Toy
+
+    description: ->
+        throw new Error "You cannot call an abstract method!"
+
+# ==============================
+# SIMPLE (CONCRETE) COMPONENT
+# ==============================
+
+# A ball does not contain anything
+class Ball extends Toy
+    description: ->
+        "There's a ball!\n"
+
+# ==============================
+# COMPOSITE (CONCRETE) COMPONENT
+# ==============================
+
+# A toy box is a toy entity which contains toys, including smaller toy boxes
+class ToyBox extends Toy
+    constructor: ->
+        @_toys = []
+
+    description: ->
+        "There's a toy box!\n"
+
+    add: (toy) ->
+        @_toys.push(toy)
+
+    inventory: ->
+        inventory = "Let's open the toy box...\n"
+        for toy in @_toys
+            inventory += toy.description()
+            if toy instanceof ToyBox
+                inventory += toy.inventory()
+        inventory
+
+# ==============================
+# CLIENT CODE
+# ==============================
+
+# Here we organize our toys in an optimal way
+ball1 = new Ball
+ball2 = new Ball
+ball3 = new Ball
+bigToyBox = new ToyBox
+smallToyBox = new ToyBox
+
+smallToyBox.add ball1
+bigToyBox.add ball2
+bigToyBox.add ball3
+bigToyBox.add smallToyBox
+
+# Now we open our big toy box...
+console.log bigToyBox.inventory()

doc/GoF/Structural/Composite/README.md

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+'use strict';
+
+// ==============================
+// ABSTRACT COMPONENT
+// ==============================
+
+var Toy = (function () {
+    function Toy() {
+        if (this.constructor === Toy) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+    }
+
+    Toy.prototype.description = function () {
+        throw new Error("You cannot call an abstract method!");
+    };
+
+    return Toy;
+})();
+
+// ==============================
+// SIMPLE (CONCRETE) COMPONENT
+// ==============================
+
+// A ball does not contain anything
+var Ball = (function () {
+    function Ball() {}
+    Ball.prototype = Object.create(Toy.prototype);
+    Ball.prototype.constructor = Ball;
+
+    Ball.prototype.description = function () {
+        return "There's a ball!\n";
+    };
+
+    return Ball;
+})();
+
+// ==============================
+// COMPOSITE (CONCRETE) COMPONENT
+// ==============================
+
+// A toy box is a toy entity which contains toys, including smaller toy boxes
+var ToyBox = (function () {
+    function ToyBox() {
+        this.toys = [];
+    }
+    ToyBox.prototype = Object.create(Toy.prototype);
+    ToyBox.prototype.constructor = ToyBox;
+
+    ToyBox.prototype.description = function () {
+        return "There's a toy box!\n";
+    };
+
+    ToyBox.prototype.add = function (toy) {
+        this.toys.push(toy);
+    };
+
+    ToyBox.prototype.inventory = function () {
+        var inventory = "Let's open the toy box...\n";
+        for (var i = 0; i < this.toys.length; i++) {
+            inventory += this.toys[i].description();
+            if (this.toys[i] instanceof ToyBox) {
+                inventory += this.toys[i].inventory();
+            }
+        }
+        return inventory;
+    };
+
+    return ToyBox;
+})();
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+// Here we organize our toys in an optimal way
+var ball1 = new Ball(),
+    ball2 = new Ball(),
+    ball3 = new Ball(),
+    bigToyBox = new ToyBox(),
+    smallToyBox = new ToyBox();
+
+smallToyBox.add(ball1);
+bigToyBox.add(ball2);
+bigToyBox.add(ball3);
+bigToyBox.add(smallToyBox);
+
+// Now we open our big toy box...
+console.log(bigToyBox.inventory());

src/CoffeeScript/GoF/Structural/Composite/Composite.coffee

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+// ==============================
+// ABSTRACT COMPONENT
+// ==============================
+
+class Toy {
+    constructor() {
+        if (new.target !== undefined) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+    }
+
+    description() {
+        throw new Error("You cannot call an abstract method!");
+    }
+}
+
+// ==============================
+// SIMPLE (CONCRETE) COMPONENT
+// ==============================
+
+// A ball does not contain anything
+class Ball extends Toy {
+    description() {
+        return "There's a ball!\n";
+    }
+}
+
+// ==============================
+// COMPOSITE (CONCRETE) COMPONENT
+// ==============================
+
+// A toy box is a toy entity which contains toys, including smaller toy boxes.
+class ToyBox extends Toy {
+    constructor() {
+        super();
+        this._toys = [];
+    }
+
+    description() {
+        return "There's a toy box!\n";
+    }
+
+    add(toy) {
+        this._toys.push(toy);   
+    }
+
+    inventory() {
+        let inventory = "Let's open the toy box...\n";
+        for (let toy of this._toys) {
+            inventory += toy.description();
+            if (toy instanceof ToyBox) {
+                inventory += toy.inventory();
+            }
+        }
+        return inventory;
+    }
+}
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+// Here we organize our toys in an optimal way
+let ball1 = new Ball(),
+    ball2 = new Ball(),
+    ball3 = new Ball(),
+    bigToyBox = new ToyBox(),
+    smallToyBox = new ToyBox();
+
+smallToyBox.add(ball1);
+smallToyBox.add(ball2);
+bigToyBox.add(ball3);
+bigToyBox.add(smallToyBox);
+
+// Now we open our big toy box...
+console.log(bigToyBox.inventory());