Declarative model/collection system in CoffeeScript

lumbar.coffee

###
# Currently based on work by Thomas Parslow
# See: https://gist.github.com/1396231
###

lumbar = 
  version: "0.0.1"

class lumbar.Model
  @field: (name, options) ->
    @fields ?= {}
    @fields[name] = options || {}
  @has_many: (klass, options) ->
    options ?= {}
    options.klass = klass
    options.as ?= klass.name.toLowerCase() + 's'
    @collections ?= {}
    @collections[options.as] = options

  constructor: (attributes) ->
    @attributes = {}
    # Copy in attributes passed in or defaults from the fields as appropriate
    for name, options of @constructor.fields
      # Defaults can be specified as values or as functions
      @attributes[name] = attributes?[name] || if (isFunction(options.default)) then options.default() else options.default
    # Set up collections
    for name,options of @constructor.collections
      @[name] = new Collection(@, options)
    @listeners = {}

  # Events
  bind: (event, listener) =>
    (@listeners[event] ?= []).push(listener)
  emit: (event, args...) =>
    listener(args...) for listener in @listeners[event] if @listeners[event]

  # Getters and setters
  get: (name) =>
    @attributes[name]
  set: (name, value) =>
    setAttribute = (name, value)
      field = @constructor.fields[name]
      throw Error('Trying to set an non-existent property!') if not field
      
      # Ignore a re-setting of the same value
      return if value == @get(name)
      @attributes[name] = value
      # Emit change events!
      @emit('change', name, value)
      @emit("change:#{name}", value)
    
    hash = {}
    if _.isObject(name) then _.extend(hash, name)
    else hash[name] = value
    
    setAttribute(name, value) for name, value of hash