Adding missing Inheritance koan file

stevehorn · stevehorn · commit 4ec938e44890 · 2010-12-31T07:37:48.000-05:00
diff --git a/koans/AboutInheritance.js b/koans/AboutInheritance.js
@@ -0,0 +1,85 @@
+function Muppet(age, hobby) {
+  this.age = age;
+  this.hobby = hobby; 
+  
+  this.answerNanny = function(){
+	return "Everything's cool!";
+  }
+}
+
+function SwedishChef(age, hobby, mood) {
+  Muppet.call(this, age, hobby);
+  this.mood = mood;
+  
+  this.cook = function() {
+    return "Mmmm soup!";
+  }
+}
+
+SwedishChef.prototype = new Muppet();
+
+describe("About inheritance", function() {
+  beforeEach(function(){
+    this.muppet = new Muppet(2, "coding");
+	this.swedishChef = new SwedishChef(2, "cooking", "chillin");
+  });
+  
+  it("should be able to call a method on the derived object", function() {
+    expect(this.swedishChef.cook()).toEqual(__);
+  });
+  
+  it("should be able to call a method on the base object", function() {
+    expect(this.swedishChef.answerNanny()).toEqual(__);
+  });
+  
+  it("should set constructor parameters on the base object", function() {
+    expect(this.swedishChef.age).toEqual(__);
+    expect(this.swedishChef.hobby).toEqual(__);	
+  });
+  
+  it("should set constructor parameters on the derived object", function() {
+    expect(this.swedishChef.mood).toEqual(__);
+  });
+});
+
+// http://javascript.crockford.com/prototypal.html
+Object.prototype.beget = function () {
+  function F() {}
+  F.prototype = this;
+  return new F();
+}
+
+function Gonzo(age, hobby, trick) {
+  Muppet.call(this, age, hobby);
+  this.trick = trick;
+  
+  this.doTrick = function() {
+    return this.trick;
+  }
+}
+
+//no longer need to call the Muppet (base type) constructor
+Gonzo.prototype = Muppet.prototype.beget();
+
+describe("About Crockford's inheritance improvement", function() {
+  beforeEach(function(){
+	this.gonzo = new Gonzo(3, "daredevil performer", "eat a tire");
+  });
+  
+  it("should be able to call a method on the derived object", function() {
+    expect(this.gonzo.doTrick()).toEqual(__);
+  });
+  
+  it("should be able to call a method on the base object", function() {
+    expect(this.gonzo.answerNanny()).toEqual(__);
+  });
+  
+  it("should set constructor parameters on the base object", function() {
+    expect(this.gonzo.age).toEqual(__);
+    expect(this.gonzo.hobby).toEqual(__);	
+  });
+  
+  it("should set constructor parameters on the derived object", function() {
+    expect(this.gonzo.trick).toEqual(__);
+  });
+});
