fields_for

# File actionpack/lib/action_view/helpers/form_helper.rb, line 712
      def fields_for(record_or_name_or_array, *args, &block)
        case record_or_name_or_array
        when String, Symbol
          name = "#{object_name}[#{record_or_name_or_array}]"
        when Array
          object = record_or_name_or_array.last
          name = "#{object_name}[#{ActionController::RecordIdentifier.singular_class_name(object)}]"
          args.unshift(object)
        else
          object = record_or_name_or_array
          name = "#{object_name}[#{ActionController::RecordIdentifier.singular_class_name(object)}]"
          args.unshift(object)
        end

        @template.fields_for(name, *args, &block)
      end