r-proto-class.js

/**
 * r-proto-class.js
 * Ruby's semantics
 *
 * Features:
 *   - super calls
 *   - using Object.create for inheritance
 *   - Class.new is a wrapper over Class.allocate and Class.initialize
 *
 * by Dmitry Soshnikov <dmitry.soshnikov@gmail.com>
 * MIT Style License
 */

var Class = {

  /**
   *allocate
   * Creates an instance. Default is
   * the implementation of native `new'
   */
  allocate: function () {
    return Object.create(this);
  },

  /**
   * new
   * A wrapper over allocated and initialize
   */
  new: function () {
    var instance = this.allocate();
    this.initialize.apply(instance, arguments);
    return instance;
  },

  /**
   * initialize
   * Configure a newly created instance
   */
  initialize: emptyFn,

  /**
   * super
   */
  super: function (method) {
    var parentName = '__' + method + '_invoke__';
    var parentObject = this[parentName];
    var proto;
    if (parentObject) {
      // deeper levels
      proto = Object.getPrototypeOf(parentObject.proto);
    } else {
      // first level (proto of an instance) -- get the next level
      proto = Object.getPrototypeOf(Object.getPrototypeOf(this));
    }
    this[parentName] = {proto: proto, level: (parentObject ? parentObject.level++ : 0)};
    var result = proto[method].apply(this, [].slice.call(arguments, 1));
    this[parentName].level--;
    if (!this[parentName].level)
      delete this[parentName];
    return result;
  }
};

console.log('--------- Point ---------\n');

// Point class
var Point = Object.create(Class, {
  initialize: {value: function (x, y) {
    console.log('Point.initialize', x, y);
    this.move(x, y);
  }},
  move: {value: function (x, y) {
    console.log('Point.move', x, y);
    this.x = x;
    this.y = y;
  }},
  toString: {value: function () {
    return 'point: '.concat(this.x, ' ', this.y);
  }},
  name: {value: "Point"}
});

var p = Point.new(10, 20);
console.log(p); // <point 10 20>

console.log('\n--------- Point3D ---------\n');

var Point3D = Object.create(Point, {
  initialize: {value: function (x, y, z) {
    this.super('initialize', x, y);
    this.z = z;
    console.log('Point3D.initialize', x, y, z);
  }},
  move: {value: function (x, y, z) {
    this.super('move', x, y);
    this.z = z;
  }},
  toString: {value: function () {
    return '3D ' + this.super('toString') + ' ' + this.z;
  }},
  name: {value: "Point3D"}
});

var p3D = Point3D.new(10, 20, 30);
console.log(p3D);

console.log('\n--------- Point4D ---------\n');

var Point4D = Object.create(Point3D, {
  initialize: {value: function (x, y, z, time) {
    this.super('initialize', x, y, z);
    this.time = time;
    console.log('Point4D.initialize', x, y, z, time);
  }},
  move: {value: function (x, y, z, time) {
    this.super('move', x, y, z);
    this.time = time;
  }},
  toString: {value: function () {
    return '4D is ' + this.super('toString') + ' + ' + this.time;
  }},
  name: {value: "Point4D"}
});

var p4D = Point4D.new(10, 20, 30, 2011);
console.log(p4D);