footnoted.rb

module Footnoted
  
  def self.included(base)
    base.class_eval do
      has_many :annotations, :as => :notable, :dependent => :delete_all
      has_one :footnote, :through => :annotations
      before_save :save_footnote
      # before_destroy :destroy_annotations
      attr_accessor :footnote_id
    end
    base.send(:include, InstanceMethods)
  end
    
  module InstanceMethods
    
    def save_footnote
      puts @footnote_id      
      return if (@footnote_id.blank? || self.id.blank?)
      Annotation.delete_all "footnote_id = #{@footnote_id} and notable_id = #{self.id}"
      note = Footnote.find_by_id(@footnote_id)
      Annotation.create(:notable => self, :footnote => note) unless note.nil?
    end
    
    def footnote_id
      self.footnote ? self.footnote.id : nil
    end    
  end 
end