Identity Map for backbone models

readme.md

I read this trick on the Soundcloud blog: http://backstage.soundcloud.com/2012/06/building-the-next-soundcloud/

You can return an existing object from a javascript constructor to avoid creating a new object. I'm using this as an identity map - one instance per id. Adapted to Coffeescript and adding a feature to update the existing class with any new information (me.set(data)), it looks something like user.coffee.

You have to copy-paste the simple return super constructor into every child class. Without this the code breaks. Not sure how to solve this issue.

user.coffee

App = {}
data_store = {}

class App.Model extends Backbone.Model
  constructor: (data)->
    name = this.__proto__.constructor.name
    if data?.id? && data_store["#{name}/#{data?.id}"]
      me = data_store["#{name}/#{data?.id}"]
      me.set(data)
      return me
    else
      super

  set: (data)->
    name = this.__proto__.constructor.name
    ret = super
    data_store["#{name}/#{@id}"] ||= @ if @id?
    ret
  
   
class App.User extends App.Model
  constructor: ()-> return super