Subclassing getters and setters in coffee-script

getter.coffee

Function::get = ($def) ->
  $name = Object.keys($def)[0]
  Object.defineProperty @::, $name, {get: $def[$name], configurable: yes}

heartofgold.coffee

class HeartOfGold

  _answer: 0

  @get answer: -> @_answer
  @set answer: (value) -> @_answer = value

setter.coffee

Function::set = ($def) ->
  $name = Object.keys($def)[0]
  Object.defineProperty @::, $name, {set: $def[$name], configurable: yes}

zaphod.coffee

class Zaphod extends HeartOfGold
 
  # Explicit access to super is used to access property behavior
  @get answer: -> Zaphod.__super__.answer * 2 * Math.PI
  @set answer: (value) -> Zaphod.__super__.answer = value
 
  constructor: (value) ->
    @answer = value
 
 
meaning_of_life = new Zaphod(6.684507609859605)
console.log "Zaphod says that the meaning of life, the universe, and everything is "+meaning_of_life.answer
 
###
$ coffee heartofgold
Zaphod says that the meaning of life, the universe, and everything is 42
###