extract invoice printing logic into a seperated method

app/jobs/bulk_invoice_job.rb

@@ -5,13 +5,7 @@ class BulkInvoiceJob < ApplicationJob
   delegate :render, to: ActionController::Base
 
   def perform(order_ids, filepath, options = {})
-    pdf = CombinePDF.new
-
-    sorted_orders(order_ids).each do |order|
-      invoice = renderer.render_to_string(order)
-
-      pdf << CombinePDF.parse(invoice)
-    end
+    sorted_orders(order_ids).each(&method(:generate_invoice)) 
 
     ensure_directory_exists filepath
 
@@ -32,6 +26,11 @@ class BulkInvoiceJob < ApplicationJob
     @renderer ||= InvoiceRenderer.new
   end
 
+  def generate_invoice order
+    invoice = renderer.render_to_string(order)
+    pdf << CombinePDF.parse(invoice)
+  end
+
   def broadcast(filepath, channel)
     file_id = filepath.split("/").last.split(".").first
 
@@ -47,4 +46,8 @@ class BulkInvoiceJob < ApplicationJob
   def ensure_directory_exists(filepath)
     FileUtils.mkdir_p(File.dirname(filepath))
   end
+
+  def pdf
+    @pdf ||= CombinePDF.new
+  end
 end