ActiveRecord: Saving IPs as 32bit signed integers

converts_addresses.rb

require 'IPAddr'

module ActiveRecord
  module Validations
    module ClassMethods

      def converts_addresses(*attributes)
        attributes.each do |attribute|
          attr_accessor "#{attribute}_addr".to_sym

          define_method("#{attribute}_addr".to_sym) do
            attribute_value = read_attribute(attribute)
            if attribute_value.nil?
              return nil
            end
            return IPAddr.new(attribute_value + 2**31, Socket::AF_INET)
          end

          define_method("#{attribute}_addr=".to_sym) do |addr|
            begin
              write_attribute(attribute, IPAddr.new(addr, Socket::AF_INET).to_i - 2**31)
            rescue ArgumentError
              write_attribute(attribute, nil)
            end
          end
        end
      end

    end
  end
end

host.rb

require 'converts_addresses'

class Host < ActiveRecord::Base
  belongs_to :subnet

  converts_addresses :ip

  validates_presence_of :ip
  validates_uniqueness_of :ip

  def validate
    Subnet.all.each do |subnet|
      if (self.ip + 2**31) & (subnet.mask + 2**31) == (subnet.network + 2**31)
        self.subnet = subnet
      end
    end

    errors.add_to_base 'There's no subnet for this IP.' if @subnet.nil?
  end
end

subnet.rb

require 'converts_addresses'

class Subnet < ActiveRecord::Base
  has_many :hosts

  converts_addresses :network, :mask

  validates_presence_of     :name
  validates_numericality_of :network,
                            :only_integer => true,
                            :greater_than_or_equal_to => -2**31,
                            :less_than => 2**31
  validates_numericality_of :mask,
                            :only_integer => true,
                            :greater_than_or_equal_to => -2**31,
                            :less_than => 2**31
  validates_uniqueness_of   :name
  validates_uniqueness_of   :network, :scope => :mask
end