Auditable, Problem with class var's

auditable.rb

# Fixed

module Auditable
  def self.included(base)
    base.extend(ClassMethods)
  end

  module ClassMethods
    def auditable(options = {})

      options[:only] ||= [:create, :update, :destroy]
      options[:if] ||= lambda { |record| true }
      options[:only_once] ||= false
      
      class_eval do
        cattr_accessor :only_once
        self.only_once = options[:only_once]
        has_one :audit_item, :as => :auditable
        after_create :audit_create, :if => options[:if] if options[:only].include?(:create)
        after_destroy :audit_destroy, :if => options[:if] if options[:only].include?(:destroy)
        after_update :audit_update, :if => options[:if] if options[:only].include?(:update)
      end
    end
  

    private

    def audit(action)
      return if self.class.only_once && self.audit_item
      AuditItem.create(:auditable => self, :tag => "#{self.class.to_s}_#{action}".downcase, :user => self.student)
    end

    def audit_create
      audit(:create)
    end

    def audit_destroy
      audit(:destroy)
    end

    def audit_update
      audit(:update) if self.changed? && self.changed != ['updated_at']
    end
  end