Export csv or excel by re-using existing HTML view

index.html.slim

table
  thead
    tr
      th = sort_link(@q, :number)
      th = sort_link(@q, :production_status)
      th = sort_link(@q, :current_step)
      th = order_name(:production_type)
      th = order_name(:type)
      th = order_name(:brand)
      th = order_name(:color)
      th = order_name(:style)
      th style="width:200px" = Order.human_attribute_name(:diagnose)
      th = sort_link(@q, :created_at)
      th = sort_link(@q, :finish_date)
      th 实际开工日期
      th 实际完工日期
  tbody
    - @orders.each do |order|
      tr
        td = link_to order.number, production_order_path(order)
        td = order.current_state_name
        td = order.current_step_name
        td = order.production_order_type
        td = order.show_item_type
        td = order.show_brand
        td = order.show_color
        td = order.show_style
        td = order.try(:full_diagnose) || order.diagnose
        td = short_date order.created_at.to_date
        td = short_date order.finish_date
        td = short_date order.actual_open_at
        td = short_date order.actual_finish_at

= paginate @orders
span.pull-right.mt20
  = page_entries_info @orders
  = download_link
  = download_link(500)

plain_helper.rb

module PlainHelper

  def download_link(per=nil)
    query = params.merge(per: per).to_query
    name =  per ?  "#{per}条" : '本页'
    link_to "导出#{name}", "#{request.path}.csv?#{query}", class: 'ml10'
  end
  
end

production_orders_controller.rb

class ProductionOrdersController < PlainController

  def index
    @q = Order.ransack(params[:q])
    @current_stop = params[:current_stop] || 'center'
    @orders = @q.result.by_stop(@current_stop).
      page(params[:page]).per(params[:per])

    respond_html_and_csv
  end

  def generate_csv_data(template = nil)
    template ||= "#{controller_name}/#{action_name}.html.slim"
    content = render_to_string(template)
    doc =  Nokogiri::HTML(content)

    table =  doc.at_css('table')
    data = table.css('tr').map do |r|
      r.css('td,th').map(&:text).to_csv
    end.join
    
    # Convert from utf8 to gbk to make it compatible with Windows Office Excel
    # And Mac number can work with GBK too
     data = data.encode('GBK', undef: :replace, replace: "")
  end

  def respond_html_and_csv
    respond_to do |format|
      format.html
      format.csv { send_data(generate_csv_data) }
    end
  end

end