Apply new order directly inside service

app/services/bulk_invoice_service.rb

@@ -7,9 +7,8 @@ class BulkInvoiceService
 
   def start_pdf_job(order_ids)
     pdf = CombinePDF.new
-    orders = Spree::Order.where(id: order_ids)
 
-    orders.each do |order|
+    orders_from(order_ids).each do |order|
       invoice = renderer.render_to_string(order)
 
       pdf << CombinePDF.parse(invoice)
@@ -29,6 +28,10 @@ class BulkInvoiceService
 
   private
 
+  def orders_from(order_ids)
+    Spree::Order.where(id: order_ids).order("completed_at DESC")
+  end
+
   def new_invoice_id
     Time.zone.now.to_i.to_s
   end

spec/services/bulk_invoice_service_spec.rb

@@ -47,4 +47,11 @@ describe BulkInvoiceService do
       expect(filepath).to eq 'tmp/invoices/1234567.pdf'
     end
   end
+
+  describe "#orders_from" do
+    it "orders with completed desc" do
+      expect(service.send(:orders_from, [1, 2]).to_sql)
+        .to include('ORDER BY completed_at DESC')
+    end
+  end
 end