url_for (ActionController::UrlWriter)

    # File lib/action_controller/url_rewriter.rb, line 52
        def url_for(options)
          options = self.class.default_url_options.merge(options)

          url = ''

          unless options.delete(:only_path)
            url << (options.delete(:protocol) || 'http')
            url << '://' unless url.match("://")

            raise "Missing host to link to! Please provide :host parameter or set default_url_options[:host]" unless options[:host]

            url << options.delete(:host)
            url << ":#{options.delete(:port)}" if options.key?(:port)
          else
            # Delete the unused options to prevent their appearance in the query string.
            [:protocol, :host, :port, :skip_relative_url_root].each { |k| options.delete(k) }
          end
          trailing_slash = options.delete(:trailing_slash) if options.key?(:trailing_slash)
          url << ActionController::AbstractRequest.relative_url_root.to_s unless options[:skip_relative_url_root]
          anchor = "##{CGI.escape options.delete(:anchor).to_param.to_s}" if options[:anchor]
          generated = Routing::Routes.generate(options, {})
          url << (trailing_slash ? generated.sub(/\?|\z/) { "/" + $& } : generated)
          url << anchor if anchor

          url
        end