application_controller.rb

def not_found
    raise ActionController::RoutingError.new('Not Found')
  rescue
    render_404
  end

  def render_404
    render file: "#{Rails.root}/app/views/errors/error404", status: :not_found
  end

  def current_user
    @current_user ||= User.find(session[:user_id]) if session[:user_id]
  end
  helper_method :current_user

  def authorize
    not_found unless current_user
  end