render_collection

# File actionview/lib/action_view/renderer/partial_renderer.rb, line 318
      def render_collection
        instrument(:collection, count: @collection.size) do |payload|
          return nil if @collection.blank?

          if @options.key?(:spacer_template)
            spacer = find_template(@options[:spacer_template], @locals.keys).render(@view, @locals)
          end

          cache_collection_render(payload) do
            @template ? collection_with_template : collection_without_template
          end.join(spacer).html_safe
        end
      end