a nice and simple version class

version.rb

class Version < ::String
  class Error < ::StandardError; end

  attr :major
  attr :minor
  attr :teeny

  def Version.default
    Version.for('0.0.0')
  end

  def Version.for(*args)
    version = args.size == 1 && args.first

    case version
      when Version
        version
      else
        Version.new(*args)
    end
  end

  def Version.numbers(version)
    Version.for(version).numbers
  end

  def initialize(*args, &block)
    super(args.flatten.join('.'))
  ensure
    @major, @minor, @teeny = strip.split(/\./).map{|v| v.to_i}
  end

  def <=> other
    numbers <=> Version.for(other).numbers
  end

  def numbers
    [major, minor, teeny]
  end

  %w( major minor teeny ).each do |number|
    module_eval <<-__, __FILE__, __LINE__

      def bump_#{ number }!
        @#{ number } += 1
        replace(numbers.join('.'))
        self
      end

      def bump_#{ number }
        dup.bump_#{ number }!
      end

    __
  end

  alias_method('bump', 'bump_minor')
  alias_method('bump!', 'bump_minor!')
end

using Gem::Version is a good idea. in my case i really needed domain specific '@version.bump!'