noproxy-association.rb

module Mongoid
  def self.included(base)
    base.extend NoProxyAssociation
  end
  
  # This little piece of codes creates an author method in Book
  # which instanciates an anonymous class with Author included!
  # def author
  #   klass = Class.new do 
  #     include Book::Author
  #   end
  #   return klass.new
  # end
  module NoProxyAssociation
    def embed_one(embeded, opt={})
      parent_class = self.to_s 
      define_method(embeded) do
        Class.new { include eval("#{parent_class}::#{embeded.to_s.capitalize}") }.new
      end
    end
  end
end

# model/book.rb
class Book
  include Mongoid
  embed_one :author, :sync => true
  embed_one :picture

  module Author
    include Mongoid
    embed_one :address
    
    def name()"Nabokov";end
    
    module Address
      def city()"Paris";end
    end
  end
  
  module Picture
    def filename()"/images/books/ada.jpg";end
  end
end

book = Book.new
puts book.author.name # => Nabokov
puts book.picture.filename # => /images/books/ada.jpg
puts book.author.address.city # => Paris