Setting the form value to an organic group gid from validation hook of custom field widget (Drupal 7)

Question

I have a custom widget which can be used for a group audience field. Instead of being a dropdown like the OG_AUDIENCE_WIDGET it is made up of three multiple select list, and the group which is actually selected is the one which is picked in the third select list. I have the actual widget working but I am stuck on validation. I have been trying to set the gid in a couple of different ways which have failed in a couple different manors. First:

function multiselect_validate($element, &$form_state)
{
  if($form_state['submitted'])
  {
    $index = array_shift(array_values($element['wrapper']['dropdown_assignment']['#value']));
    $assignment_name = $element['wrapper']['dropdown_assignment']['#options'][$index];
    $query = new EntityFieldQuery();
    $result = $query
    ->entityCondition('entity_type', 'node')
    ->entityCondition('bundle', 'assignment_group')
    ->propertyCondition('title',$assignment_name)    
    ->execute();
    $node  = reset($result['node']);
    $assignment_gid = og_get_group("node", $node->nid)->gid;
    $value = $value[LANGUAGE_NONE][0]['gid'] = $assignment_gid;
    form_set_value($element,array('gid'=>198), $form_state);
  }
}

This kind of validation returns an error:

[11-Dec-2012 11:23:07] PHP Fatal error:  Cannot unset string offsets in /Applications/MAMP/htdocs/arcade/modules/field/field.default.inc on line 41

I also tried something like this for the final form_set_value:

form_set_value($element,array('gid'=>$assignment_gid), $form_state);

But when I do this and then look at the result nothing actually gets set into the field.

What is the proper way to set the gid for the field?

Answer 1

I'm assuming the validate callback that you have mentioned in your question is the #element_validate callback for the field widget element.

In that case, form_set_value must be set to a list of items because a field is inherently multi-valued. Each item in this list must conform to the schema of the field.

So, in this case:

$items = array();
$delta = 0;
$gid = ...; // From somewhere
$items[$delta] = array(
  'gid' => $gid,
  'state' => OG_STATE_ACTIVE, // optional
  'created' => REQUEST_TIME - 3600 // optional (yesterday)
);
form_set_value($element, $items, $form_state);

To illustrate this better, I have a sandbox project up on drupal.org. It declares a new widget with hierarchical dropdowns just like you have described. You can check the code directly from http://drupalcode.org/sandbox/amarnus/1868742.git/tree/refs/heads/master or clone the project from http://drupal.org/sandbox/amarnus/1868742. Hope this helps!