class RobotsController < ApplicationController DEFAULT_FILENAME = 'config/robots.txt'.freeze def robots filename = if subdomain && subdomain != 'www' "config/robots.#{ subdomain }.txt" end file_to_render = File.exists?(filename.to_s) ? filename : DEFAULT_FILENAME render file: file_to_render, layout: false, content_type: 'text/plain' end private def subdomain request.subdomain.present? ? request.subdomain : nil end end