Extract to class ExchangeVariantDeleter

app/controllers/spree/admin/products_controller_decorator.rb

@@ -50,7 +50,7 @@ Spree::Admin::ProductsController.class_eval do
 
     delete_stock_params_and_set_after do
       super
-      remove_product_from_order_cycles if original_supplier != @product.supplier_id
+      ExchangeVariantDeleter.new.delete(@product) if original_supplier != @product.supplier_id
     end
   end
 
@@ -193,13 +193,6 @@ Spree::Admin::ProductsController.class_eval do
     end
   end
 
-  def remove_product_from_order_cycles
-    variant_ids = @product.variants.map(&:id)
-    ExchangeVariant.
-      where(variant_id: variant_ids).
-      delete_all
-  end
-
   def set_product_master_variant_price_to_zero
     @product.price = 0 if @product.price.nil?
   end

app/models/spree/product_set.rb

@@ -54,7 +54,7 @@ class Spree::ProductSet < ModelSet
     end
     product.save if errors.empty?
 
-    remove_product_from_order_cycles(product) if original_supplier != product.supplier_id
+    ExchangeVariantDeleter.new.delete(product) if original_supplier != product.supplier_id
   end
 
   def validate_presence_of_unit_value(product, variant)
@@ -64,13 +64,6 @@ class Spree::ProductSet < ModelSet
     product.errors.add(:unit_value, "can't be blank")
   end
 
-  def remove_product_from_order_cycles(product)
-    variant_ids = product.variants.map(&:id)
-    ExchangeVariant.
-      where(variant_id: variant_ids).
-      delete_all
-  end
-
   def update_product_variants(product, attributes)
     return true unless attributes[:variants_attributes]
     update_variants_attributes(product, attributes[:variants_attributes])

app/services/exchange_variant_deleter.rb

@@ -0,0 +1,8 @@
+class ExchangeVariantDeleter
+  def delete(product)
+    variant_ids = product.variants.map(&:id)
+    ExchangeVariant.
+      where(variant_id: variant_ids).
+      delete_all
+  end
+end