Mongomapper sortable list

gistfile1.rb

# Allow for sortable lists in mongomapper
# fairly application specific but just to show an example...
module MongoMapper; module Plugins
  module SortableQuestion
    extend ActiveSupport::Concern
  
    included do
      key :position, Integer, :default => 1
      before_create :append_to_bottom_of_list
      after_destroy :set_lower_sibling_positions
    end
    
    module ClassMethods
            
      def reorder_pages(*pages)
        pages.each_with_index do |ids, index|
          set(*ids, {:page_number => index + 1})
        end
      end
      
      def reorder(*ids, page_number)
        ids.map! {|id| id.to_s } # ensure entities are strings 
        ids.each_with_index do |id, index|
          set(id, {:position => index + 1, :page_number => page_number})
        end
      end
      
    end
    
    def previous
      self.survey.questions.first(:position => position - 1, :page_number => page_number)
    end

    def next
      self.survey.questions.first(:position => position + 1, :page_number => page_number)
    end 
    
    # @todo
    def set_position(index, options = {})
      
    end
    
    def siblings
      self.survey.questions.all(:page_number => self.page_number, :position.ne => self.position)
    end
    
    private 
    def append_to_bottom_of_list
      self.position = self.survey.questions.all(:page_number => self.page_number).count + 1 
    end 

    def set_lower_sibling_positions
      Question.decrement({:survey_id => self.survey_id, :position.gt => self.position, :page_number => self.page_number}, {:position => 1})
    end 
  end  
end; end