Re-use renderer object

app/services/bulk_invoice_service.rb

@@ -10,7 +10,7 @@ class BulkInvoiceService
     orders = Spree::Order.where(id: order_ids)
 
     orders.each do |order|
-      invoice = InvoiceRenderer.new.render_to_string(order)
+      invoice = renderer.render_to_string(order)
 
       pdf << CombinePDF.parse(invoice)
     end
@@ -37,6 +37,10 @@ class BulkInvoiceService
     'tmp/invoices'
   end
 
+  def renderer
+    @renderer ||= InvoiceRenderer.new
+  end
+
   def file_directory
     Dir.mkdir(directory) unless File.exist?(directory)
     directory