Programmatically delete one entry from one field on one entity

Question

What's the proper way to programmatically delete one specific field entry for a multi-entry field from one specific entity? (that's specific fields and specific entities, not field types or instances and entity types)

Here's some possibilities I've looked into which don't work:

• Loading the entity with entity_load(), setting the field entry to =null or =array(), then saving with field_attach_update(). It's the closest I've found but it leaves a zombie null field entry in the database which shows up as a blank row on forms until the form is saved and hook_field_is_empty() can kick in (hook_field_is_empty() is configured such that =null or =array() will flag as empty).
• Loading the entity with entity_load(), unsetting the field entry by key, then saving with field_attach_update(). This seems to do nothing - it seems that Drupal interprets the entry not being there as a sign to not modify it. (strangely I also sometimes get maximum query time expiration timeouts when trying this approach)
• field_attach_delete() - this is much too blunt: it kills all fields for the entity
• field_purge_data() - better, but still too blunt: it kills all entries of the field, not specific entries

So to clarify, I've got code that finds (and loads) an entity which has a field that has multiple entries, and finds a specific entry on that field that needs to be removed. I want to remove that entry completely, without touching any other entries or any other fields on the entity.

Answer 1

If you're able to rely on the entity API module you should be able to use code similar to the following:

// Load some entity.
$entity = entity_load_single($entity_type, $id);

// Remove the field value.
unset($entity->field_FIELD_NAME[LANGUAGE_NONE][$index]);

// Reset the array to zero-based sequential keys.
$entity->field_FIELD_NAME[LANGUAGE_NONE] = array_values($entity->field_FIELD_NAME[LANGUAGE_NONE]);

// Save the entity.
entity_save($entity_type, $entity);

Answer 2

I needed to do this as part of a Drupal8 migration cleanup.

After some experimentation, I found that iterating and then using unset() on the delta could kill it. My example was removing a tag (hence I search for 'target_id', not 'value' as you often would for other fields.

/**
 * Removes a term from a field.
 *
 * @return bool
 *   success
 */
private function removeTerm(\Drupal\node\NodeInterface $object, \Drupal\taxonomy\TermInterface $term, $field_name) {
  // Check if tag value exists already.
  // Remember they may be multiples.
  /** @var @var \Drupal\Core\Field\FieldItemList $field_values */
  $field_values = $object->get($field_name);
  foreach ($field_values as $delta => $field_value) {
    if ($field_value->getValue()['target_id'] == $term->id()) {
      unset($field_values[$delta]);
      return TRUE;
    }
  }
  return FALSE;
}

And afterwards, if success, then $object->save();

Answer 3

For Drupal 8, to delete a field from an entity:

$entity = Node::load($nid);
unset($entity->field_name);

This will call the magic method __unset() from ContentEntityBase:

public function __unset($name) {
    // Unsetting a field means emptying it.
    if ($this->hasField($name)) {
        $this->get($name)->setValue([]);
    }
    // For non-field properties, unset the internal value.
    else {
        unset($this->values[$name]);
    }
}

Don't forget that, to persist your changes, you need to call

$entity->save();

After you've done all your changes.

Answer 4

This is better way:

> $user = user_load($user->uid); 
> $user_wrp = entity_metadata_wrapper('user', $user);
> $user_wrp->{'field_data_multiple'} = array();

Answer 5

the current preferred method would employ the entity_metadata_wrapper

$node_wrapped = entity_metadata_wrapper('node', node_load($nid));

unset($node_wrapped->$field_name[$index];

this is the best tutorial on the EMW that i've seen http://deeson-online.co.uk/labs/programatically-access-field-data-using-entitymetadatawrapper-drupal