Add Bridge (ES5 + ES6 + CoffeeScript)

Author: Badacadabra

doc/GoF/Structural/Bridge/Bridge.dia

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+# Synopsis
+
+I do not know what to eat for dinner. In my kitchen, I think I have pasta and rice with some sauces, especially pesto and carbonara.
+
+# Problem
+
+Even in this very simple situation, they are already four recipes that could be great. I can eat pasta with pesto, pasta with carbonara, risotto with pesto, or risotto with carbonara.
+
+To represent that with code, we may want to use inheritance, which is not really convenient. If we use inheritance, we will have a "class" for each possible recipe (PastaWithPesto, PastaWithCarbonara, RisottoWithPesto, RisottoWithCarbonara). But imagine that, a couple of minutes later, you also find potatoes and a tomato sauce in the kitcken. Do you really want to create new classes such as PotatoesWithCarbonara, PastaWithTomato and so on?
+
+# Solution
+
+Here we need to split the hierarchy of classes and prefer composition over inheritance. We will then use a Bridge between a simple recipe and a sauce. This means that we will be able to select the sauce independently. To do so, we may have:
+
+  * An abstract class (Recipe) with a reference to another abstraction, generally an interface (Sauce)
+  * Concrete implementations of both abstractions
+  
+Of course, methods defined in the main abstract class delegate operations to the methods of the other abstraction.

doc/GoF/Structural/Bridge/Bridge.png

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+# ==============================
+# ABSTRACTIONS
+# ==============================
+
+class Recipe
+    constructor: (sauce) ->
+        throw new Error "You cannot instantiate an abstract class!" if @constructor is Recipe
+        @_sauce = sauce   
+
+    cook: ->
+        throw new Error "You cannot call an abstract class!"
+
+class Sauce
+    constructor: ->
+        throw new Error "You cannot call an abstract method!" if @constructor is Sauce
+
+    ingredients: ->
+        throw new Error "You cannot call an abstract method!"
+
+# ==============================
+# CONCRETE RECIPES
+# ==============================
+
+class Pasta extends Recipe
+    cook: ->
+        "Pasta with #{@_sauce.ingredients()}"
+
+class Risotto extends Recipe
+    cook: ->
+        "Risotto with #{@_sauce.ingredients()}"
+
+# ==============================
+# CONCRETE SAUCES
+# ==============================
+
+class Pesto extends Sauce
+    ingredients: ->
+        "Pesto (basil, garlic, oil, grated cheese, pine nuts)"
+
+class Carbonara extends Sauce
+    ingredients: ->
+        "Carbonara (eggs, bacon, black pepper, grated cheese)"
+
+# ==============================
+# CLIENT CODE
+# ==============================
+
+# Sauces
+pesto = new Pesto
+carbonara = new Carbonara
+
+# Recipes
+pasta = new Pasta pesto
+risotto = new Risotto carbonara
+
+console.log pasta.cook()
+console.log risotto.cook()

doc/GoF/Structural/Bridge/README.md

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+'use strict';
+
+// ==============================
+// ABSTRACTIONS
+// ==============================
+
+var Recipe = (function () {
+    function Recipe(sauce) {
+        if (this.constructor === Recipe) {
+            throw new Error("You cannot instantiate an abstract class!");
+        } 
+        this._sauce = sauce;
+    }
+
+    Recipe.prototype.cook = function() {
+        throw new Error("You cannot call an abstract method!");
+    };
+
+    return Recipe;
+})();
+
+var Sauce = (function () {
+    function Sauce() {
+        if (this.constructor === Sauce) {
+            throw new Error("You cannot instantiate an abstract class!");
+        } 
+    }
+
+    Sauce.prototype.ingredients = function() {
+        throw new Error("You cannot call an abstract method!");
+    };
+
+    return Sauce;
+})();
+
+// ==============================
+// CONCRETE RECIPES
+// ==============================
+
+var Pasta = (function () {
+    function Pasta(sauce) {
+        Recipe.call(this, sauce);
+    }
+    Pasta.prototype = Object.create(Recipe.prototype);
+    Pasta.prototype.constructor = Pasta;
+
+    Pasta.prototype.cook = function () {
+        return "Pasta with " + this._sauce.ingredients(); 
+    };
+
+    return Pasta;
+})(); 
+
+var Risotto = (function () {
+    function Risotto(sauce) {
+        Recipe.call(this, sauce);
+    }
+    Risotto.prototype = Object.create(Recipe.prototype);
+    Risotto.prototype.constructor = Risotto;
+
+    Risotto.prototype.cook = function () {
+        return "Risotto with " + this._sauce.ingredients(); 
+    };
+
+    return Risotto;
+})(); 
+
+// ==============================
+// CONCRETE SAUCES
+// ==============================
+
+var Pesto = (function () {
+    function Pesto() {}
+    Pesto.prototype = Object.create(Sauce.prototype);
+    Pesto.prototype.constructor = Pesto;
+
+    Pesto.prototype.ingredients = function () {
+        return "Pesto (basil, garlic, oil, grated cheese, pine nuts)";
+    };
+
+    return Pesto;
+})();
+
+var Carbonara = (function () {
+    function Carbonara() {}
+    Carbonara.prototype = Object.create(Sauce.prototype);
+    Carbonara.prototype.constructor = Carbonara;
+
+    Carbonara.prototype.ingredients = function () {
+        return "Carbonara (eggs, bacon, black pepper, grated cheese)";
+    };
+
+    return Carbonara;
+})();
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+// Sauces
+var pesto = new Pesto(),
+    carbonara = new Carbonara();
+
+// Recipes
+var pasta = new Pasta(pesto),
+    risotto = new Risotto(carbonara);
+
+console.log(pasta.cook());
+console.log(risotto.cook());

src/CoffeeScript/GoF/Structural/Bridge/Bridge.coffee

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+// ==============================
+// ABSTRACTIONS
+// ==============================
+
+class Recipe {
+    constructor(sauce) {
+        if (new.target !== undefined) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+        this._sauce = sauce;   
+    }
+
+    cook() {
+        throw new Error("You cannot call an abstract class!");
+    }
+}
+
+class Sauce {
+    constructor() {
+        if (new.target !== undefined) {
+            throw new Error("You cannot call an abstract method!");
+        }
+    }
+
+    ingredients() {
+        throw new Error("You cannot call an abstract method!");
+    }
+}
+
+// ==============================
+// CONCRETE RECIPES
+// ==============================
+
+class Pasta extends Recipe {
+    cook() {
+        return "Pasta with " + this._sauce.ingredients();
+    }
+}
+
+class Risotto extends Recipe {
+    cook() {
+        return "Risotto with " + this._sauce.ingredients();
+    }
+}
+
+// ==============================
+// CONCRETE SAUCES
+// ==============================
+
+class Pesto extends Sauce {
+    ingredients() {
+        return "Pesto (basil, garlic, oil, grated cheese, pine nuts)"; 
+    }
+}
+
+class Carbonara extends Sauce {
+    ingredients() {
+        return "Carbonara (eggs, bacon, black pepper, grated cheese)";
+    }
+}
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+// Sauces
+let pesto = new Pesto(),
+    carbonara = new Carbonara();
+
+// Recipes
+let pasta = new Pasta(pesto),
+    risotto = new Risotto(carbonara);
+
+console.log(pasta.cook());
+console.log(risotto.cook());