initialize `@renderer` to avoid ivar warnings

1 files changed, 8 insertions, 1 deletions

diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index d054450853..5055a88217 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -13,13 +13,20 @@ module ActionController
 
       RENDERER_LOCK = Mutex.new
 
-      # Returns a renderer class (inherited from ActionController::Renderer)
+      attr_writer :renderer
+
+      # Returns a renderer instance (inherited from ActionController::Renderer)
       # for the controller.
       def renderer
         @renderer || RENDERER_LOCK.synchronize do
           @renderer ||= Renderer.for(self)
         end
       end
+
+      def inherited(klass)
+        klass.renderer = nil
+        super
+      end
     end
 
     # Before processing, set the request formats in current controller formats.