Playing with CoffeeScript, do funny things with mixins.

gistfile1.coffee

# Swappable Mixins in CoffeeScript
# ================================

# This is experimental. Not tested. It's just a toy, and I'm very new to
# javascript/coffeescript. Be warned.


# Usage
# -----

#     class MyMixin extends Mixin
#       foo: ->
#     
#     obj = {bar: ->}
#     
#     MyMixin:: augment obj
#     
#     obj.foo   # -> [function]
#     obj.bar   # -> [function]
#     
#     obj.eject MyMixin
#     
#     obj.foo   # -> undefined
#     obj.bar   # -> [function]


# Mixin
# -----

# Classes inheriting `Mixin` will become removable mixins, enabling you to
# swap them around.
class Mixin

  # "Class method". Augment object or class `t` with new methods.
  augment: (t) ->
    (t[n] = m unless n == 'augment' or !this[n].prototype?) for n, m of this

  # When an object is augmented with at least one mixin, call this method to
  # remove `mixin`.
  eject: (mixin) ->
    (delete this[n] if m in (p for o, p of mixin::)) for n, m of this


# Limitations
# -----------

# * When a class is augmented, all instances of that class are augmented too,
#   and when a mixin is ejected from a class, all instances lose that mixin
#   too.
# * You can't eject a mixin from an object if that mixin was added to the
#   object's class. Eject the mixin from the class instead.
# * Only methods can be mixed-in, attributes are ignored.