RoR-like ApplicationController for CI... how?

[eluser]oscaralexander[/eluser]
I'm very new to CI but have done some RoR development in the past. RoR provides developers with a basic ApplicationController which is initialized (once, I believe) at each request. So, say you call /blog/view/my-post, it first instantiates the ApplicationController and executes whatever code you put inside its constructor.

I used this controller to check whether the user is logged in and make user data available to the view, prior to executing the requested controller/action (i.e. /blog/view/my-post). This was convenient since I needed user data in 90% of the views, across different controllers.

What is the CI way of doing this? Sub-classing the Controller and autoloading it? Hooks?

Please help