ActiveAdmin custom csv file method

collection_action :csv_isp_report, method: :get do

      @data = []

      @isp_manuall = $record_arr

      @isp_manuall.map{|isp_manuall| isp_manuall.map { |isp| @data << isp}}

      @data_records = @data

      csv_string = CSV.generate do |csv|

        csv << IspReport.attribute_names

        @data_records.each do |ispr|

          csv << ispr.attributes.values

        end

      end

      send_data csv_string 

  end

in View

= link_to "CSV", csv_isp_report_admin_isp_reports_path(format: "csv")