2 files changed, 21 insertions, 13 deletions
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 7f7fb90d87..3d35b5bb6f 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -83,6 +83,7 @@ module ActiveModel
   # in-place attributes.
   #
   #   person.name_will_change!
+  #   person.name_change    # => ['Bill', 'Bill']
   #   person.name << 'y'
   #   person.name_change    # => ['Bill', 'Billy']
   module Dirty
diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index f3781f7a68..f5ea285ccb 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -110,17 +110,24 @@ module ActiveModel
         end
     end
 
-    private
-      # Fires notifications to model's observers
-      #
-      # def save
-      #   notify_observers(:before_save)
-      #   ...
-      #   notify_observers(:after_save)
-      # end
-      def notify_observers(method)
-        self.class.notify_observers(method, self)
-      end
+    # Fires notifications to model's observers
+    #
+    #   def save
+    #     notify_observers(:before_save)
+    #     ...
+    #     notify_observers(:after_save)
+    #   end
+    #
+    # Custom notifications can be sent in a similar fashion:
+    #
+    #   notify_observers(:custom_notification, :foo)
+    #
+    # This will call +custom_notification+, passing as arguments
+    # the current object and :foo.
+    #
+    def notify_observers(method, *extra_args)
+      self.class.notify_observers(method, self, *extra_args)
+    end
   end
 
   # == Active Model Observers
@@ -230,10 +237,10 @@ module ActiveModel
 
     # Send observed_method(object) if the method exists and
     # the observer is enabled for the given object's class.
-    def update(observed_method, object, &block) #:nodoc:
+    def update(observed_method, object, *extra_args, &block) #:nodoc:
       return unless respond_to?(observed_method)
       return if disabled_for?(object)
-      send(observed_method, object, &block)
+      send(observed_method, object, *extra_args, &block)
     end
 
     # Special method sent by the observed class when it is inherited.