One url with multiple controllers

Lets say that I want to have one url that can map to two different controllers. For example /posts could map to controller 'public/ posts' or to the controller 'admin/posts' based on whether or not the user has logged in. This isn't a great example because I could just use '/admin/posts', but in my scenario the url has to be the same.

I was hoping to use a before_filter to either render one action or the other. It looks like render_component would have let me accomplish this, but it has been deprecated.

Thanks! Tom