how to check session with a filter?

Hey all, I have a simple session checker function in my application.rb: def check_session unless !session[:state].nil? redirect_to :controller => ‘users’, :action => ‘login’ end end

I would like to apply that function to some actions only of my ‘machines’ controller which are edit,update,create,new and destroy. I know it has something to do with before_filter but I’m not sure how to use it.

any idea?

thanx in advance