when using mongoid, id not an integer

venshop_app/app/models/product.rb

@@ -22,7 +22,7 @@ class Product
   validates :user, presence: true
   validates :name, :code, :condition, :image_medium, :price, presence: true
   validates :name, length: { maximum: 255 }
-  validates :price, :product_category_id, numericality: true
+  validates :price, numericality: true
   validates :price_currency, presence: true, if: "price > 0"
 
   include Sunspot::Mongoid