charge.coffee

Spine      = require('spine')
Accounting = require('accounting')

class Charge extends Spine.Model
  @key 'amount', required: true
  @key 'description'
  @key 'token'
  @key 'status'
  @key 'outgoing', Boolean
  @key 'created_at', Date
  @key 'updated_at', Date

  @url: '/charges'
  @extend Spine.Model.Ajax

  dollarAmount: (value) ->
    @amount = Accounting.unformat(value) * 100 if value?
    (@amount or 0) / 100

module.exports = Charge

If @url is a param to Spine.Model.Ajax mixin why not just pass it directly:

...
@extend new Spine.Model.Ajax(url: '/charges')
...

Love the @key syntax!

Reminds me of mongoose. Like it and I'm curious how this will be further implemented. Validation would become a bit more elegant.