A Rails mixin to make inquiries with lookup tables, e.g. when used in association

lookup_table.rb

# Mix this into an AR class for lookup tables to perform an inquiry.
# For example, if Movie has Genre and genres table has id->genre mapping
# then one could use the_movie.genre.comedy? instead of the_movie.genre.genre == 'comedy'
module LookupTable
  def self.included(base)
    raise "#{name} can only be included into classes that inherit from ActiveRecord::Base, #{base.name} does not." unless base < ActiveRecord::Base

    base.instance_variable_set :@lookup_column, base.name.demodulize.underscore
    base.extend(ClassMethods)
  end

  module ClassMethods
    attr_reader :lookup_column

    # Reverse find
    def rfind(value)
      where(lookup_column => value).take
    end
  end

  private

  def respond_to_missing?(method_name, include_private = false)
    (method_name[-1] == "?") || super
  end

  def method_missing(method_name, *arguments)
    if method_name.to_s[-1, 1] == "?"
      val = read_attribute self.class.lookup_column
      val == method_name.to_s[0..-2]
    else
      super
    end
  end
end