Delegate #code to shipment_method

core/app/models/spree/shipping_rate.rb

@@ -6,6 +6,7 @@ class ShippingRate < Spree::Base
 
     delegate :order, :currency, to: :shipment
     delegate :name, to: :shipping_method
+    delegate :code, to: :shipping_method, prefix: true
 
     def display_base_price
       Spree::Money.new(cost, currency: currency)
@@ -41,9 +42,5 @@ def display_price
     def display_tax_amount(tax_amount)
       Spree::Money.new(tax_amount, currency: currency)
     end
-
-    def shipping_method_code
-      shipping_method.code
-    end
   end
 end