A quick dictionary module

change_type.rb

class ChangeType < ActiveRecord::Base
  attr_accessible :listing_change_id, :name
  include Dictionary
  build_dictionary :addition, :deletion, :reservation, :reservation_withdrawal
end

dictionary.rb

module Dictionary

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

  module ClassMethods
    #builds a set of constants like: KEY = 'KEY'
    #as well as a method self.dict that returns all of those constants' values
    def build_dictionary *keys
      keys.each do |key|
        const_set key.to_s.upcase, key.to_s.upcase
      end
      define_singleton_method("dict") { keys.map{|k| k.to_s.upcase } }
    end
  end
end