Download file programmatically

Question

I have a custom module where I need to create a file and download it on form submission. So far, I managed to created the file and save it in public folder, but I cannot find a way to download it to client. This is the code I wrote so far.

public function submitForm(array &$form, FormStateInterface $form_state) {
  $file_name = $date.'-event.ics';
  $cal_file = file_unmanaged_save_data('file content',"public://cal/$file_name",FILE_EXISTS_RENAME);
  return new RedirectResponse(file_create_url("public://cal/211443-event.ics"));
}

Answer 1

You can return a BinaryFileResponse from a controller, or as 4k4 has added:

$response = new BinaryFileResponse("public://cal/211443-event.ics");
$form_state->setResponse($response);

Answer 2

That is what, for example, the Drupal\locale\Form\ExportForm class does. See the code used in ExportForm::submitForm().

$response = new BinaryFileResponse($uri);
$response->setContentDisposition('attachment', $filename);
$form_state->setResponse($response);

$response->setContentDisposition() sets the Content-Disposition header with the given filename. That is the filename used for the Save file dialog the browser will show to users.