I'm trying to save the site that a user came from when they sign up. Right now I have a before_filter in my ApplicationController:

before_filter :save_referer

  def save_referer
    unless is_logged_in?
      session['referer'] = request.env["HTTP_REFERER"] unless session['referer']
    end
  end

Then when a user is created, it checks this session variable and sets it to nil. Sometimes this does not work and I'm worried there might be some unintended things happening with using session like this. Does anyone have a better way? Or some input perhaps?

EDIT: This is the logic I am using to save the referer:

def create
@user = User.new(params[:user])
if @user.save_with(session[:referer]) .... end

User def save_with(referer) self.referer = referer unless referer == "null" self.save
end

Is there any reason why this should not work?