model add scope

app/models/product.rb

@@ -115,13 +115,13 @@ class Product < ActiveRecord::Base
     def after_destroy
         clean_share_img
     end
-    strs=""
+    mer=""
     def gross_interest_rate
         rate = 0
         if self.buy_price != 0 && self.price != 0
             rate = (( self.price.to_f - self.buy_price.to_f )/self.buy_price.to_f)*100
         end
-        mer =field :gross_interest_rate do
+        mer=field :gross_interest_rate do
             formatted_value{bindings[:view].current_admin_user.email}
         end
         return mer