I got this error when I upload/remove a file. This is caused because the render function requires a variable passed by reference. So the fix is to change the lines of code to this:

file.inc/image.inc line 90:
$render = $function($entity_type, $entity, $field, $instance, $langcode, array($item), $display);
$element['dragndrop_uploads'] = array(
'#type' => 'hidden',
'#value' => render($render),

Comments

mavin773’s picture

mavin773 commented
Priority: Normal » Major

I would love to see turned into a patch and sent upstream, but sadly the poster is proposing modification of a CORE module and not Drag'n'Drop Uploads.

Johnny vd Laar’s picture

Johnny vd Laar commented

file.inc and image.inc are part of Drag 'n drop uploads module. (inside the modules folder).

mavin773’s picture

mavin773 commented

Oh. :P

blanca.esqueda’s picture

blanca.esqueda commented
Issue summary: View changes

I've created a patch that includes the fix for this issue.

Please check:
https://www.drupal.org/node/2043627#comment-9911113

blanca.esqueda’s picture

blanca.esqueda commented
Related issues: +#2043627: Error Notice: Notice: Undefined index: [field name] in file_dragndrop_uploads_process() (line 63... /moduels/file.inc
blanca.esqueda’s picture

blanca.esqueda commented

I got the same/similar error again, when adding a file fields to comments.

Strict warning: Only variables should be passed by reference in file_dragndrop_uploads_process() (line 92 of /var/www/drupal/sites/all/modules/contrib/dragndrop_uploads/modules/file.inc).
Warning: unlink(/var/www/drupal/sites/default/files/test.txt): Operation not permitted in drupal_unlink() (line 2282 of /var/www/drupal/includes/file.inc).

Applied the same patch and it worked.