basic computed properties in backbone

computed.coffee

Namespace.models.Base = Backbone.Model.extend
  initialize: ()->
    Backbone.Model::initialize @, arguments

    return if _.isUndefined(@computed)

    @_computed = {}

    for attr, dependencies of @computed
      @on "change:#{attr}", ()=>
        @_computed[attr] = @[attr].call @

      _(dependencies).each (dep)=>
        @on "change:#{dep}", ()=>
          @trigger "change:#{attr}"
        @trigger "change:#{attr}" if @has(dep)

  get: (attr)->
    if @computed?.hasOwnProperty(attr)
      @_computed[attr]
    else
      Backbone.Model::get.call @, attr

Namespace.models.Example = Namespace.models.Base.extend
  computed:
    fullName: ['firstName', 'lastName']

  fullName: ()->
    "#{@get('firstName')} #{@get('lastName')}"

Can you please elaborate?
Here is working fiddle example if you want to fiddle with it: http://jsfiddle.net/Cpn3g/247/
Update: To support initial setting of the models via constructor http://jsfiddle.net/Cpn3g/250/

There are many ways to do it, it's all about pros, cons and personal preferences - to me this seems more complex and doesn't add much value.
I'm not suggesting it doesn't work, however there are a bunch of issues with it:

• Changing the convention of a model (adding extra methods) is something i try to avoid (smells like home brew).
• Adding extra model properties with trailing underscore can have side effects.
• This will throw when you try to `model.set({fullName: 'some random name'});
• In general, I think events are a non issue and we should not bind to computed properties events

Cool, thanks

Greetings,

Here is a small function that implements computed properties for Backbone https://github.com/curran/backboneComputedProperties .

Regards,
Curran