Change autocomplete path with hook_form_alter()

Question

I'm trying to change the autocomplete path of a node reference field (References module) with a custom module using hook_form_alter().
I have no problem changing any property of the field except the ["#autocomplete_path']. when I set another value for this, the field loses its autocomplete feature. (The hidden autocomplete field isn't there anymore as well) I find this totally weird, and haven't found anything about this in issue queues or anything like that.

Just FYI, I've setup a new MENU_CALLBACK path with hook_menu() and a callback function, so I'll be able to return JSON suggestions depending on some custom parameters and the value of another field.

Answer 1

On a stock installation of Drupal 7 and references 7.x-2.0-beta3 I was able to use the following form alter to successfully change the autocomplete path for a node reference field on the article content type:

function YOURMODULE_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'article_node_form') {
    $form['field_node_ref'][LANGUAGE_NONE][0]['nid']['#autocomplete_path'] = 'another/url';
  }
}

Another option is to ignore the form and use hook_menu_alter to change the callback for node_reference/autocomplete/%/%/%. Your callback should accept $entity_type, $bundle, $field_name which you can use to filter out which requests you want to respond to.

Answer 2

You should ensure your custom callback function is fetching correct json response. we can do so by calling the page callback path from the browser itself.

If its correct then check, The last param is always string in the page callback function which you need not to mention in form_alter or in hook_menu path but drupal will add the last param automatically while calling the function. I guess you missed the last param in your case.

Menu callback function should be like :

  $items['autocomplete/node/%'] = array(
      'title' => 'Custom autocomplete node reference',
      'page callback' => 'pms_custom_node_autocomplete',
      'page arguments' => array(**2**),
      'access callback' => TRUE,
      'type' => MENU_CALLBACK,
  );

Page callback function should be like :

function pms_custom_node_autocomplete($node_type, $string = "") {
  // Get $string here to use in LIKE statement or whatever.
}

Answer 3

In my own case (D7.20), I had to set my hook_form_alter() like that:

function module_form_alter(&$form, &$form_state, $form_id){
    if ($form_id == "event_node_form"){
        $form['field_event_location']['und'][0]['value']['#autocomplete_path'] = 'module/autocomplete';
        return $form;
    }
}