1 files changed, 19 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute.rb b/activerecord/lib/active_record/attribute.rb
index f78cde23c5..8604ccb90d 100644
--- a/activerecord/lib/active_record/attribute.rb
+++ b/activerecord/lib/active_record/attribute.rb
@@ -29,6 +29,14 @@ module ActiveRecord
       type.type_cast_for_database(value)
     end
 
+    def changed_from?(old_value)
+      type.changed?(old_value, value, value_before_type_cast)
+    end
+
+    def changed_in_place_from?(old_value)
+      type.changed_in_place?(old_value, value)
+    end
+
     def type_cast
       raise NotImplementedError
     end
@@ -52,5 +60,16 @@ module ActiveRecord
         type.type_cast_from_user(value)
       end
     end
+
+    class Null
+      class << self
+        attr_reader :value, :value_before_type_cast, :value_for_database
+
+        def changed_from?(*)
+          false
+        end
+        alias changed_in_place_from? changed_from?
+      end
+    end
   end
 end