Observers not longer add an after_find method to the observed class.

[#625 state:resolved]

activerecord/lib/active_record/observer.rb

@@ -20,7 +20,7 @@ module ClassMethods
       #   ActiveRecord::Base.observers = Cacher, GarbageCollector
       #
       # Note: Setting this does not instantiate the observers yet. +instantiate_observers+ is
-      # called during startup, and before each development request.  
+      # called during startup, and before each development request.
       def observers=(*observers)
         @observers = observers.flatten
       end
@@ -130,11 +130,11 @@ def inherited(subclass)
   # Observers register themselves in the model class they observe, since it is the class that
   # notifies them of events when they occur. As a side-effect, when an observer is loaded its
   # corresponding model class is loaded.
-  # 
+  #
   # Up to (and including) Rails 2.0.2 observers were instantiated between plugins and
-  # application initializers. Now observers are loaded after application initializers, 
+  # application initializers. Now observers are loaded after application initializers,
   # so observed models can make use of extensions.
-  # 
+  #
   # If by any chance you are using observed models in the initialization you can still
   # load their observers by calling <tt>ModelObserver.instance</tt> before. Observers are
   # singletons and that call instantiates and registers them.
@@ -189,7 +189,6 @@ def observed_subclasses
 
       def add_observer!(klass)
         klass.add_observer(self)
-        klass.class_eval 'def after_find() end' unless klass.method_defined?(:after_find)
       end
   end
 end

activerecord/test/cases/lifecycle_test.rb

@@ -143,12 +143,20 @@ def test_observing_subclasses
     assert_equal developer.name, multi_observer.record.name
   end
 
-  def test_observing_after_find_when_not_defined_on_the_model
+  def test_after_find_cannot_be_observed_when_its_not_defined_on_the_model
     observer = MinimalisticObserver.instance
     assert_equal Minimalistic, MinimalisticObserver.observed_class
 
     minimalistic = Minimalistic.find(1)
-    assert_equal minimalistic, observer.minimalistic
+    assert_nil observer.minimalistic
+  end
+
+  def test_after_find_can_be_observed_when_its_defined_on_the_model
+    observer = TopicObserver.instance
+    assert_equal Topic, TopicObserver.observed_class
+
+    topic = Topic.find(1)
+    assert_equal topic, observer.topic
   end
 
   def test_invalid_observer