Class.create prototype not properly subclassed

Question

So, I'm trying to expand the google map class, specifically google.maps.OverlayView (in version 3). Executing this vanilla js method fully works.

POIOverlay = function(marker, poi, type) { this._marker = marker; this._poi = poi; this._type = type; this._div = null; this.latlng_ = marker.getPosition(); this._map = marker.getMap(); this._offsetVertical = -195; this._offsetHorizontal = 0; this._height = 165; this._width = 266; } POIOverlay.prototype = new google.maps.OverlayView(); POIOverlay.prototype.create = function() { console.log(this) } POIOverlay.prototype.draw = function() { //stuff } 

However, making this a prototype, you cannot add any of the methods of the parent class:

 POIOverlay = Class.create(new google.maps.OverlayView(), { initialize : function(marker, poi, type) { this._marker = marker; this._poi = poi; this._type = type; this._div = null; this.latlng_ = marker.getPosition(); this._map = marker.getMap(); this._offsetVertical = -195; this._offsetHorizontal = 0; this._height = 165; this._width = 266; }, create : function() { if(this._div) return; console.log(this); }, draw : function() { //stuff } }); 

Here is the code to create / use the class:

  try { poio = new POIOverlay(marker,poi,type); } catch(e) { console.log(e); } google.maps.event.addListener(marker, 'click', poio.draw.bind(poio) ); 

In the first example, the console registers an object with parent and child methods / attributes. In the second example, the console registers an object without parent attributes / methods.

Obviously, this is not a big deal, but I was wondering if anyone else had this problem, and if it is easy to fix. I am using prototype 1.7.

Answer 1

The argument of the superclass should be the proper prototype of the "Class" - remember that classes do not actually exist in JavaScript. There are several classic inheritance models for JavaScript, and you should be able to get a prototype chain (including a link to the parent "class" and prototype) by manually creating proxy servers and prototypes.

From prototype class.js :

[[Class.create]] accepts two types of arguments. If the first argument is [[Class]], it is used as the superclass of the new class, and all its methods are inherited. Otherwise, any arguments passed are treated as objects and their methods are copied (“mixed”) as methods of the instance of the new class.