application.rb

  before_filter :auth
  
  helper_method :current_user

  # Authorise user if possible
  def auth
    if session[:user_id].nil? then
      @current_user = User.guest
    else
      @current_user = User.find(session[:user_id])      
    end
  end
  
  def current_user
    @current_user
  end
  
  # Require login
  def require_login
    redirect_to '/login' if @current_user.guest?
  end