access current_user in an Observer

gistfile1.rb

class ApplicationController < ActionController::Base
before_filter :set_current_user
private
def set_current_user
  UserActionObserver.current_user = current_user
end
end

class UserActionObserver < ActiveRecord::Observer
  # assuming these all have created_by_id and updated_by_id
  observe Product, Thing, OtherThing

  cattr_accessor :current_user

  def before_create(model)
    model.created_by = @@current_user
  end

  def before_update(model)
    model.updated_by = @@current_user
  end
end