Add Chain of Responsibility (ES5 + ES6 + CoffeeScript + TypeScript)

Author: Badacadabra

doc/GoF/Behavioral/ChainOfResponsibility/ChainOfResponsibility.dia

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+# Synopsis
+
+Imagine a long relay race with athletes from different sports. This race could involve several teams composed each time of a racewalker, a runner and a swimmer.
+
+# Problem
+
+Each sport has its own rules and each athlete will participate differently. So we cannot just evaluate the role of each athlete in the same way, even though the objective is the same for everyone within a team: the gold medal. A swimmer and a runner are both athletes, but a swimmer swims whereas a runner runs... Here we could say that each team member handles a part of the initial request which is to win the race.
+
+Moreover, this is a relay race, not an individual one. Each athlete must know the next relay where another athlete will wait for the baton before to start.
+
+# Solution
+
+Everytime a request should be handled by multiple (and complementary) processing units, the Chain of Responsibility pattern seems ideal. In this case, this pattern requires:
+
+  * An abstract representation of a racer (abstract class or interface)
+  * Concrete racers (Walker, Runner, Swimmer)
+  * Composition because each racer "class" must have a reference to the next relay (except for the last athlete who crosses the finish line)

doc/GoF/Behavioral/ChainOfResponsibility/ChainOfResponsibility.png

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+# ==============================
+# ABSTRACT RACER 
+# ==============================
+
+class Racer
+    constructor: ->
+        throw new Error "You cannot instantiate an abstract class!" if @constructor is Racer
+
+    go: ->
+        res = ""
+        if @nextRelay? then res += @nextRelay.go() else res += ""
+        res
+
+    setNextRelay: (relay) ->
+        @nextRelay = relay
+
+# ==============================
+# CONCRETE RACERS
+# ==============================
+
+class Walker extends Racer
+    go: ->
+        "Walker: go!\n#{super}"
+
+class Runner extends Racer
+    go: ->
+        "Runner: go!\n#{super}"
+
+class Swimmer extends Racer
+    go: ->
+        "Swimmer: go!\n#{super}"
+
+# ==============================
+# CLIENT CODE
+# ==============================
+
+walker = new Walker
+runner = new Runner
+swimmer = new Swimmer
+
+walker.setNextRelay runner
+runner.setNextRelay swimmer
+
+console.log walker.go()

doc/GoF/Behavioral/ChainOfResponsibility/README.md

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+// ==============================
+// ABSTRACT RACER 
+// ==============================
+
+abstract class Racer {
+    protected nextRelay: Racer;
+
+    public go(): string {
+        var res = "";
+        if (this.nextRelay === undefined) {
+            res += "";
+        } else {
+            res += this.nextRelay.go();
+        }
+        return res;
+    }
+
+    public setNextRelay(relay: Racer): void {
+        this.nextRelay = relay;
+    }
+}
+
+// ==============================
+// CONCRETE RACERS
+// ==============================
+
+class Walker extends Racer {
+    public go(): string {
+        return `Walker: go!\n${super.go()}`;
+    }
+}
+
+class Runner extends Racer {
+    public go(): string {
+        return `Runner: go!\n${super.go()}`;
+    }
+}
+
+class Swimmer extends Racer {
+    public go(): string {
+        return `Swimmer: go!\n${super.go()}`;
+    }
+}
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+let walker: Racer = new Walker(),
+    runner: Racer = new Runner(),
+    swimmer: Racer = new Swimmer();
+
+walker.setNextRelay(runner);
+runner.setNextRelay(swimmer);
+
+console.log(walker.go());

src/CoffeeScript/GoF/Behavioral/ChainOfResponsibility/ChainOfResponsibility.coffee

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+'use strict';
+
+// ==============================
+// ABSTRACT RACER 
+// ==============================
+
+var Racer = (function() {
+    function Racer() {
+        if (this.constructor === Racer) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+    }
+
+    Racer.prototype.go = function () {
+        var res = "";
+        if (this.nextRelay === undefined) {
+            res += "";
+        } else {
+            res += this.nextRelay.go();
+        }
+        return res;
+    };
+
+    Racer.prototype.setNextRelay = function (relay) {
+        this.nextRelay = relay;
+    };
+
+    return Racer;
+})();
+
+// ==============================
+// CONCRETE RACERS
+// ==============================
+
+var Walker = (function () {
+    function Walker() {}
+    Walker.prototype = Object.create(Racer.prototype);
+    Walker.prototype.constructor = Walker;
+
+    Walker.prototype.go = function () {
+        return "Walker: go!\n" + Racer.prototype.go.call(this);
+    };
+
+    return Walker;
+})();
+
+var Runner = (function () {
+    function Runner() {}
+    Runner.prototype = Object.create(Racer.prototype);
+    Runner.prototype.constructor = Runner;
+
+    Runner.prototype.go = function () {
+        return "Runner: go!\n" + Racer.prototype.go.call(this);
+    };
+
+    return Runner;
+})();
+
+var Swimmer = (function () {
+    function Swimmer() {}
+    Swimmer.prototype = Object.create(Racer.prototype);
+    Swimmer.prototype.constructor = Swimmer;
+
+    Swimmer.prototype.go = function () {
+        return "Swimmer: go!\n" + Racer.prototype.go.call(this);
+    };
+
+    return Swimmer;
+})();
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+var walker = new Walker(),
+    runner = new Runner(),
+    swimmer = new Swimmer();
+
+walker.setNextRelay(runner);
+runner.setNextRelay(swimmer);
+
+console.log(walker.go());

src/TypeScript/GoF/Behavioral/ChainOfResponsibility/ChainOfResponsibility.ts

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+// ==============================
+// ABSTRACT RACER 
+// ==============================
+
+class Racer {
+    constructor() {
+        if (new.target !== undefined) {
+            throw new Error("You cannot instantiate an abstract class!");
+        }
+    }
+
+    go() {
+        let res = "";
+        if (this.nextRelay === undefined) {
+            res += "";
+        } else {
+            res += this.nextRelay.go();
+        }
+        return res;
+    }
+
+    setNextRelay(relay) {
+        this.nextRelay = relay;
+    }
+}
+
+// ==============================
+// CONCRETE RACERS
+// ==============================
+
+class Walker extends Racer {
+    go() {
+        return `Walker: go!\n${super.go()}`;
+    }
+}
+
+class Runner extends Racer {
+    go() {
+        return `Runner: go!\n${super.go()}`;
+    }
+}
+
+class Swimmer extends Racer {
+    go() {
+        return `Swimmer: go!\n${super.go()}`;
+    }
+}
+
+// ==============================
+// CLIENT CODE
+// ==============================
+
+let walker = new Walker(),
+    runner = new Runner(),
+    swimmer = new Swimmer();
+
+walker.setNextRelay(runner);
+runner.setNextRelay(swimmer);
+
+console.log(walker.go());