class Snippet include MongoMapper::Document key :name, String, :required => true, :index => true key :parent_name, String, :required => true, :index => true key :parent_id, ObjectId, :required => true, :index => true key_i18n :content, String before_validation :setup_default_value validates_uniqueness_of :name, :scope => :parent_id protected def setup_default_value self.parent_id = Item.find_by_name( self.parent_name ).id end end