Fetching files and generate zip file

In a recent project, written in Ruby on Rails, I wanted to fetch files from a CDN and zip them for a user to download. I thought I'd share it here for future folks:

def generate_zip
  filename = "filename.zip"
  temp_file = Tempfile.new(filename)
  files_to_zip = []
  # This is the tricky part
  # Initialize the temp file as a zip file
  Zip::OutputStream.open(temp_file) { |zos| }

  # Add files to the zip file as usual
  Zip::File.open(temp_file.path, Zip::File::CREATE) do |_zip|
    file_urls.each do |file_url|
      file_to_zip = get_document_for_zip(file_url)
      files_to_zip << file_to_zip
      _zip.add('some file name', file_to_zip)
    end
  end

  # Read the binary data from the file
  zip_data = File.open(temp_file.path)

  # Send the data to the browser as an attachment
  # We do not send the file directly because it will
  # get deleted before rails actually starts sending it

  zip_data
rescue StandardError => e
  # do something
ensure
  temp_file.close
  temp_file.unlink
  files_to_zip.each do |file_to_zip|
    file_to_zip.close
    file_to_zip.unlink
  end
end


def get_document_for_zip(file_url)
  file_to_zip = Tempfile.new('some file name')
  file_to_zip.binmode
  file_to_zip.write(HTTParty.get(file_url))
  file_to_zip.flush
  file_to_zip
end

Then in your controller

def export
respond_to do |format|
  format.zip do
          send_data generate_zip, filename: "filename.zip", type: "application/zip"
  end
end

That should do the trick!