gistfile1.coffee

  decorate: (n, fn) ->
    target = this[n]

    unless _.isFunction target
      throw new Error "Can't decorate #{n}, it's not a Function."

    unless target.fns?
      wrap = ->
        args   = Array.prototype.slice.call arguments
        finish = _.after wrap.fns.length, => wrap.old.apply this, args

        _.each wrap.fns, (fn) => fn.call this, finish

      _.extend wrap, fns: [], old: target
      this[n] = target = wrap

    target.fns.push fn

    this