How do I in code add new field values to a D8 content entity?

Question

How do I in code, create a new field value, add it to a content entity, and then have it saved to the DB?

Field API is dead. Long live Entity Field API! clearly shows how to read values, but doesn't mention inserts/updates.

Answer 1

I'm not sure what you mean with "field value", do you mean field items with multiple values?

It's the same as reading them, nothing special:

// Those are identical, not specifying [0] results in that using by default.
$entity->some_field->value = 'Whatever';
$entity->some_field[0]->value = 'Whatever';

// To add a value for the second item:
$entity->some_field[1]->value = 'Something';

// And persist to DB:
$entity->save();

Edit, the following script works for me and gives me the following output:

<?php
use Drupal\node\Entity\Node;

$node = Node::create(array('type' => 'article'));
$node->field_tags->target_id = 5;
var_dump($node->field_tags->getValue());

$node->field_tags[] = 6;
$node->field_tags[] = array('target_id' => 7);
var_dump($node->field_tags->getValue());

unset($node->field_tags[1]);
var_dump($node->field_tags->getValue());

Output:

array(1) {
  [0] =>
  array(1) {
    'target_id' =>
    int(5)
  }
}
array(3) {
  [0] =>
  array(1) {
    'target_id' =>
    int(5)
  }
  [1] =>
  array(1) {
    'target_id' =>
    int(6)
  }
  [2] =>
  array(1) {
    'target_id' =>
    int(7)
  }
}
array(2) {
  [0] =>
  array(1) {
    'target_id' =>
    int(5)
  }
  [2] =>
  array(1) {
    'target_id' =>
    int(7)
  }
}

The delta is off then in the last example, but this will probably be fixed in https://www.drupal.org/node/2164601, which might also affect how the code above works..

Answer 2

Here's what I've ended up doing. In my examples, I'm adding and removing an entity reference.

How to add a new field value:

// Insert a new field value:
$field = 'field_name';
$fieldItems = $entity->$field->getValue();

$entity->$field->setValue(
  array_merge(
    $entity->$field->getValue(),
    array($target_entity)
  )
);
$entity->save();

I found no way of removing field items directly, so instead I overwrite all of them.

// Removing a field value. In this example, an entity reference.
foreach ($fieldItems as $delta => $fieldItem) {
  if ($fieldItem['target_id'] === $target_entity_id) {
    unset($fieldItems[$delta]);
    $entity->$field->setValue($fieldItems);
    $entity->save();
    break;
  }
}