modularize.rb

require "active_support/inflector"

module Modularizable

  def modularize(target, params={})
    ancestors = params[:in] || []
    ancestors << target 
    ancestors.collect { |item| item.to_s.camelize }.join("::").constantize
  end

end

module UserPermissions

  extend Modularizable

  def self.factory(role)
    modularize role, :in => [:user_permissions, :roles]
  end

  module Roles

    module Admin;end
    module Guest;end

  end

end

puts UserPermissions.factory :admin # => UserPermissions::Roles::Admin
puts UserPermissions.factory :guest # => UserPermissions::Roles::Guest