hstore on rails

attribute_field.rb

# all including models requires column named 'data' of type hstore
module Extensions
  module AttributeField
    extend ActiveSupport::Concern

    included do
      class_attribute :attributes
      self.attributes = Hash.new {|k,v| k[v] = []}
    end

    module ClassMethods

      # data columns keys always as strings!
      def field(name)
        self.attributes[self] << name


        class_eval do
          define_method name do
            data[name.to_s] if data.present?
          end

          define_method "#{name}=" do |new_value|
            self.data = {} if data.nil?
            self.data[name.to_s] = new_value
          end
        end
      end

      def available_attributes
        klasses = self.ancestors.select {|klass| klass <= Item}
        klasses.inject([]) do |memo, klass|
          memo += attributes[klass]
        end
      end
    end
  end
end

model.rb

class Aircraft < AircraftType
  include Extensions::AttributeField

  # this will create fields that are stored in hstore column (named data) but accessible as normal AR columns
  field :serial_number
  field :registration
end