before_filter_login_example.rb

class UsersController < ApplicationController
  before_filter :set_current_user, :except => [:login, :process_login]
  private # subsequent methods are private to this class, until 'public' given
  def is_logged_in?
    redirect_to login_path and return unless (@current_user = get_logged_in_user)
  end
  public
  # ...controller actions go here
end