How to redirect back to the page after user Login?

Hello all,

I am using acts_as_authenticated as my login system.

it does a good job redirecting back to where the user were after
login, when using the controller action fliter.

however if i use a link in my page to link to the login page, it
doesn't redirect back to where the user were after login.

i have a look at the code of AAA, it uses
   1. redirect_back_or_default(:controller => '/account', :action =>
'index')
   2.
   3. #code for redirect_back_or_default
   4. def redirect_back_or_default(default)
   5. session[:return_to] ?
redirect_to_url(session[:return_to]) : redirect_to(default)
   6. session[:return_to] = nil
   7. end
to redirect back to the origin page.

how and where to set the session[:return] in my app to make it
redirect back to the origin page after login?

Thanks all.