corrected sample code to clear @_current_user class variable also

railties/guides/source/action_controller_overview.textile

@@ -239,7 +239,7 @@ class LoginsController < ApplicationController
   # "Delete" a login, aka "log the user out"
   def destroy
     # Remove the user id from the session
-    session[:current_user_id] = nil
+    @_current_user = session[:current_user_id] = nil
     redirect_to root_url
   end
 end