Extending is expensive. Delegating is usually cheaper, just be careful how you do it. https://gist.github.com/4441557 https://gist.github.com/4441557 I guess

Extending is expensive. Delegating is usually cheaper, just be careful how you do it. https://gist.github.com/4441557 https://gist.github.com/4441557 I guess the upside of `extend` is that you can do it at the call site, delegation has to be configured upfront.