Add Facade (ES5 + ES6 + CoffeeScript)

Author: Badacadabra

doc/GoF/Structural/Facade/Facade.dia

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+# Synopsis
+
+I love my pets but, due to Alzheimer's disease, I often forget how to feed them. Any help would be appreciated. 
+
+# Problem
+
+The more pets you have, the more difficult it will be to remember the menu for each animal. Complexity can grow quite fast, which is not ideal in terms of code (re)usability. We should keep it simple, stupid (KISS).
+
+# Solution
+
+Facade is often used to hide the underlying complexity of a system. To implement this design pattern, we can:
+
+  * Create an abstract representation of an Animal (abstract class or interface)
+  * Create concrete implementations of this abstraction (Dog & Rabbit)
+  * Create a "class" that will make it easy to use the concrete implementations (HowToFeedAnimals)

doc/GoF/Structural/Facade/Facade.png

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+"use strict"
+
+# ==============================
+# ABSTRACT ANIMAL
+# ==============================
+
+class Animal
+    constructor: ->
+        throw new Error "You cannot instantiate an abstract class!" if @constructor is Animal
+
+    eat: ->
+        throw new Error "You cannot call an abstract method!"
+
+# ==============================
+# CONCRETE ANIMALS
+# ==============================
+
+class Dog extends Animal
+    eat: ->
+        "Dog: 'Meat, please!'\n"
+
+class Rabbit extends Animal
+    eat: ->
+        "Rabbit: 'A carrot would be great!'\n"
+
+# ==============================
+# THE FACADE 
+# ==============================
+
+class HowToFeedAnimals
+    constructor: ->
+        @_dog = new Dog
+        @_rabbit = new Rabbit
+
+    feedAnimals: ->
+        "#{@_dog.eat()} #{@_rabbit.eat()}"
+
+# ==============================
+# CLIENT CODE
+# ==============================
+
+facade = new HowToFeedAnimals
+
+console.log facade.feedAnimals()

doc/GoF/Structural/Facade/README.md

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+'use strict';
+
+// ==============================
+// ABSTRACT ANIMAL
+// ==============================
+
+var Animal = (function () {
+    function Animal() {
+        if (this.constructor === Animal) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+    }
+
+    Animal.prototype.eat = function () {
+        throw new Error("You cannot call an abstract method!");
+    };
+
+    return Animal;
+})();
+
+// ==============================
+// CONCRETE ANIMALS
+// ==============================
+
+var Dog = (function () {
+    function Dog() {}
+    Dog.prototype = Object.create(Animal.prototype);
+    Dog.prototype.constructor = Dog;
+
+    Dog.prototype.eat = function () {
+        return "Dog: 'Meat, please!'\n";
+    };
+
+    return Dog;
+})();
+
+var Rabbit = (function () {
+    function Rabbit() {}
+    Rabbit.prototype = Object.create(Animal.prototype);
+    Rabbit.prototype.constructor = Rabbit;
+
+    Rabbit.prototype.eat = function () {
+        return "Rabbit: 'A carrot would be great!'\n";
+    };
+
+    return Rabbit;
+})();
+
+// ==============================
+// THE FACADE 
+// ==============================
+
+var HowToFeedAnimals = (function () {
+    var dog = new Dog(),
+        rabbit = new Rabbit();
+
+    function HowToFeedAnimals() {}
+
+    HowToFeedAnimals.prototype.feedAnimals = function () {
+        return dog.eat() + rabbit.eat();
+    };
+
+    return HowToFeedAnimals;
+})();
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+var facade = new HowToFeedAnimals();
+
+console.log(facade.feedAnimals());

src/CoffeeScript/GoF/Structural/Facade/Facade.coffee

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+// ==============================
+// ABSTRACT ANIMAL
+// ==============================
+
+class Animal {
+    constructor() {
+        if (new.target !== undefined) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+    }
+
+    eat() {
+        throw new Error("You cannot call an abstract method!");
+    }
+}
+
+// ==============================
+// CONCRETE ANIMALS
+// ==============================
+
+class Dog extends Animal {
+    eat() {
+        return "Dog: 'Meat, please!'\n";
+    }
+}
+
+class Rabbit extends Animal {
+    eat() {
+        return "Rabbit: 'A carrot would be great!'\n";
+    }
+}
+
+// ==============================
+// THE FACADE 
+// ==============================
+
+class HowToFeedAnimals {
+    constructor() {
+        this._dog = new Dog();
+        this._rabbit = new Rabbit();
+    }
+
+    feedAnimals() {
+        return `${this._dog.eat()} ${this._rabbit.eat()}`;
+    }
+}
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+var facade = new HowToFeedAnimals();
+
+console.log(facade.feedAnimals());