ruby on rails 3 - Accessing a url directly without login -

i considering doing -

any url (excecpt disallow specifically) can accessed directly without signing-in, if click on of links on page, redirect sign-up page

i thinking of several ways of doing it, neither flexible enough work devise

create new link_to_not_registered helper use on every link_to , check if user logged in or not
create before_filter check if user logged in. bit problematic, don't know how create filter when linking , not when directly accessing page
have external flag test if user logged in , change page accordingly.

neither way helps me redirect user after sign-in/sign (new helper links sign up, before filter becomes complex, flags simple)

is there way create functionality of direct access show actions while clicking on links requires login?

i think best approach before_filter. can check previous page request.referrer, if it's page inside app, redirect user signin path

def to_signin     redirect_to singin_path if request.referrer["http://myapp.com"] end

EXIT