orbit-4-1/app/models/snippet.rb

class Snippet
  
   include MongoMapper::Document
  
   key :name, String, :required => true, :index => true
   key :parent_name, String, :required => true, :index => true
   key :parent_id, String, :required => true, :index => true
   
   key_i18n :content, String
   
   before_validation :setup_default_value
   
   protected

   def setup_default_value
     self.parent_id = Item.find_by_name( self.parent_name ).id
   end   
   
end