How to create zip files on the fly w/o Tempfile

There are many articles about how to archive files from the server and send a zip-file to a client without persisting it on the server. But usually they don't literally do it, because they use temporary files.

There is a simple way to do it without creating any file though. You just have to put files directly to Zip::OutputStream and then read from it. Btw pay attention: you must rewind the stream before reading it.

# some files objects

def download(files)

  zip_stream = Zip::OutputStream.write_buffer do |zip|

    files.each.with_index(1) do |file, index|

     # file name must be uniq in archive

      zip.put_next_entry("#{file.name}--#{index}.#{file.extension}")

      zip.write(file.read.force_encoding('utf-8'))

    end

  end

  # important - rewind the steam

  zip_stream.rewind

  send_data zip_stream.read, 

            type: 'application/zip', 

            disposition: 'attachment', 

            filename: 'files-archive.zip'

end