How can I configure rails routing rules based on hostname?

Hello,

I would like to configure rails routing rules based on hostname.  From browsing the web I tried adding the following code to my environment.rb:

module ActionController
  module Routing
    class RouteSet
      def extract_request_environment(request)
        { :method => request.method, :hostname => request.server_name }
      end
    end
    class Route
      alias_method :old_recognition_conditions, :recognition_conditions
      def recognition_conditions
        result = old_recognition_conditions
        result << "conditions[:hostname] === env[:hostname]" if conditions[:hostname]
        Rails.logger.debug "result = #{result}"
        result
      end
    end
  end
end

Then in my routes.rb, I added:
  map.connect ':id', :controller => 'landing', :action => 'index', :conditions => { :hostname => 'blah' }

Yet the routing rule seems to be enacted regardless of the hostname.  Furthermore the debug code I added to recognition_conditions never seems to get called.