Nested attributes hack

nested_attributes_hack.rb

module Addons
  module HashNestedAttributes
    extend ActiveSupport::Concern

    # My own nested attributes to create a cleaner interface
    # when sending nested attributes from a javascript app
    module ClassMethods
      def accepts_hash_nested_attributes_for relation_name, options = {}
        relation_class = relation_name.to_s.classify.safe_constantize

        define_method "#{relation_name}_hash=" do |records|
          relation_collector = self.send(relation_name).to_a

          new_ids = records.map {|rec| rec[:id].to_i }
          old_ids = relation_collector.map(&:id)
          relation_class.where(:id => old_ids - new_ids).delete_all

          records.map do |rec|
            rec    = rec.symbolize_keys
            record = self.send(relation_name).detect { |m| m.id == rec[:id].to_i }
            if record
              record.update_attributes(rec)
            else
              if !options[:reject_if] || (options[:reject_if].present? && !options[:reject_if].call(rec))
                self.send(relation_name).build(rec)
              end
            end
          end
        end
      end
    end
  end                                                                                                                                                                            
end