if_in_controller.rb

class ApplicationController < ActionController::Base
	
  before_filter do
    if (Subdomain)
      @site = Site.find_by_name!(request.subdomain)
    end
  end
	
end

# located in /lib and included via a require in /config/application.rb
# this code works when called elsewhere
class Subdomain
  def self.matches?(request)
    request.subdomain.present? && request.subdomain != "www"
  end
end