Bring Property model from spree core

app/models/spree/property.rb

@@ -0,0 +1,21 @@
+module Spree
+  class Property < ActiveRecord::Base
+    has_and_belongs_to_many :prototypes, join_table: 'spree_properties_prototypes'
+
+    has_many :product_properties, dependent: :destroy
+    has_many :products, through: :product_properties
+
+    attr_accessible :name, :presentation
+
+    validates :name, :presentation, presence: true
+
+    scope :sorted, -> { order(:name) }
+
+    def self.find_all_by_prototype(prototype)
+      id = prototype
+      id = prototype.id if prototype.class == Prototype
+      joins("LEFT JOIN properties_prototypes ON property_id = #{self.table_name}.id").
+        where(prototype_id: id)
+    end
+  end
+end