Rails 4 ...在send_data之后重新加载页面

Question

我在控制器中有一个方法export_csv。

def export_csv
   if params[:from_date].present? && params[:to_date].present?
   @users = User.where("created_at between ? and ?", params[:from_date], params[:to_date])
        if !@users.blank?
            users_csv = User.to_excel(@users)
            send_data(users_csv, :type => 'text/csv', :filename => 'users.csv')
            flash.now[:success] = "Successfully downloaded the report!"
       else
        flash.now[:notice] = "No records over selected duration!"
       end
   else
    flash.now[:notice] = "Select from and to date.."
   end
end

文件已下载，但页面未刷新或重新加载。因此，即使在下载文件后，flash消息仍保持在页面上。

我浏览过几个网站，发现send_data会自动渲染视图，因此无法使用其他重定向或渲染。

有没有办法在send_data之后重新加载页面。？

Answer 1

send_data设置整个服务器响应，因此浏览器只接收CSV文件，而不是网页。这就是您的Flash消息未显示的原因。另一种方法是生成一个临时CSV文件（带有随机名称）并提供一个链接：

def export_csv
   if params[:from_date].present? && params[:to_date].present?
   @users = User.where("created_at between ? and ?", params[:from_date], params[:to_date])
        if !@users.blank?
            #Create temporary CSV report file and get the path to it.
            csv_file_path = create_csv_file(User.to_excel(@users))

            #Change the flash message a bit for requesting the user
            #to click on a link to download the file.                
            flash.now[:success] = "Your report has been successfully generated! Click <a href='#{csv_file_path}'>here</a> to download".html_safe
       else
        flash.now[:notice] = "No records over selected duration!"
       end
   else
    flash.now[:notice] = "Select from and to date.."
   end
end

当然你应该实现函数create_csv_file。为了避免在服务器中保留旧文件，您可以实现一种新方法，例如download_report将读取文件，使用send_data发送回客户端并最终将其删除。

修改

上述功能的伪代码：

require 'tempfile'

def create_csv_file(data)       
    #Create a temporary file. If you omit the second argument of Tempfile.new
    #then the OS's temp directory will be used.
    tmp = Tempfile.new('report', 'my/temp/dir')
    tmp.write(data)
    tmp.close

    return tmp.path
end


#Method in controller for downloading the file. I omit checks and/or security issues.
def download_report
    #Warning: a mechanism should be implemented to prevent the remote 
    #client from faking the path and download other files. 
    #A possible solution would be providing not only the file path but also a
    #hash with a secret key to validate the path. Function create_csv_file()
    #should, then, return a hash in addition of a path.

    path = params[:report] 
    file = File.open(path, "rb")
    contents = file.read
    file.close

    send_data(contents , :type => 'text/csv', :filename => 'users.csv')       
    file.unlink #Delete file
end