Get parent of an entity reference

Question

I have an entity reference inside node. How can I retrieve the parent node?

I tried with the following code, where $node is my entity reference, but it doesn't work.

$entity_ids = $query
    ->condition('type', 'user')
    ->condition('status', 1)
    ->condition('field_product_document', $node->getTitle(),'CONTAINS');

What is wrong in the code? What code should I use?

Answer 1

An entity reference field is implemented from the \Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem class. If you look at the code for EntityReferenceItem::preSave(), you will notice it is setting its target_id property to $this->entity->id().

public function preSave() {
  if ($this->hasNewEntity()) {
    // Save the entity if it has not already been saved by some other code.
    if ($this->entity->isNew()) {
      $this->entity->save();
    }
    // Make sure the parent knows we are updating this property so it can
    // react properly.
    $this->target_id = $this->entity->id();
  }
  if (!$this->isEmpty() && $this->target_id === NULL) {
    $this->target_id = $this->entity->id();
  }
}

I take your code should be changed to the following one.

$entity_ids = $query
    ->condition('type', 'user')
    ->condition('status', 1)
    ->condition('field_product_document', $node->id());

The change makes also sense: A node title cannot be used to uniquely identify a node, since there could be more nodes with the same title; the node ID uniquely identify a node on a Drupal site.

Answer 2

Here is how to do it with entityTypeManager:

$parent_node_results = \Drupal::entityTypeManager()
  ->getListBuilder('node')
  ->getStorage()
  ->loadByProperties([
    'type' => $bundle,
    'status' => 1,
    'field_child_nodes' => $node->id(), //the reference field on the parent
   ]
);

if($parent_node_results) {
  // $parent_node_results is an associative array of parent_id=>parent_entity.
  $parent_node_id = key($parent_node_results);
  $parent_node = $parent_node_results[$parent_node_id];
}

Answer 3

You should be able to get the referenced entity using

$parent = $node->field_product_document->entity;