gistfile1.rbx

module HasAttributesFor
  module ActiveRecord
    def self.included(ar)
      ar.extend ClassMethods
    end

    module ClassMethods
      def has_attributes_for(association)
        primary_key_name = reflect_on_association(association).primary_key_name
        
        class_eval %{
          def #{association}_attributes=(params)
            @original_#{association} ||= #{association}.clone

            existing = new_record? ? {} : #{association}.index_by(&:id)

            keep = []
            
            (params||[]).each do |attributes|
              id = attributes[:id].to_i
              if id && r = existing[id]
                r.attributes = attributes.except(:id)
              else
                # we use build so that it doesn't save the record yet instead of <<
                r = #{association}.build(attributes.except(:id))
              end

              keep << r
            end

            # remove all the original records that were no longer referenced
            # this will not actually delete these records, only unreference them
            deletions = self.#{association} - keep
            
            deletions.each do |r|
              # important to use target here to remove the record from memory but not the database
              self.#{association}.target.delete(r)
            end
          end
        }
        
        class_eval %{
          def original_#{association}
            @original_#{association}
          end
          
          def original_#{association}=(value)
            @original_#{association} = value
          end
        }, __FILE__, __LINE__
        
        class_eval %{
          before_update do |p|
            if p.original_#{association}
              new_records = p.#{association}
              p.original_#{association}.each do |r|
                p.#{association}.delete(r) unless new_records.member?(r)
              end
            end
            
            p.#{association}.each do |r|
              if r.changed?
                r.#{primary_key_name} = p.id
                r.save
              end
            end
          end
          
          after_save do |p|
            p.original_#{association} = nil
          end
        }, __FILE__, __LINE__
        
      end
    end
    
  end
    
  
end