Metaprogramación con Coffescript

metaprograming_example.coffee

Function::hasProperties = (properties) ->
  self = @
  self.prototype.properties = {}
  definePropertie = (key, value) ->
    self.prototype.properties[key] = value
    self.prototype[key] = (newValue) ->
      @properties[key] = newValue
      @
  for key, value of properties
    definePropertie key, value

class CoffeeCup
  @hasProperties
    strength: 'medium'
    cream: false
    sugar: false
  toString: ->
    "#{@properties.strength} - #{@properties.cream} - #{@properties.sugar}"

morningCup = new CoffeeCup()
morningCup.properties

eveningCup =
  new CoffeeCup().
  strength('dark').
  cream(true).
  sugar(true)

alert eveningCup.toString()