Using resource controller and namespace

app/controllers/spree/admin/digitals_controller.rb

@@ -0,0 +1,15 @@
+module Spree
+  class Admin::DigitalsController < Spree::Admin::ResourceController
+    belongs_to "spree/product", find_by: :permalink
+    
+    def load_resource
+      @object = @product = Product.find_by_permalink(params[:product_id])
+    end
+
+    
+    protected
+      def location_after_save
+        admin_product_digitals_url(@product)
+      end
+  end
+end