Merge pull request #368 from Earlopain/tweak-memoize-good

Tweak find-by-memoization good example

Author: koic

README.adoc

@@ -1160,11 +1160,9 @@ end
 
 # good
 def current_user
-  if instance_variable_defined?(:@current_user)
-    @current_user
-  else
-    @current_user = User.find_by(id: session[:user_id])
-  end
+  return @current_user if defined?(@current_user)
+
+  @current_user = User.find_by(id: session[:user_id])
 end
 ----