Programmatically append values to entity reference field of node with a dynamic field name

Question

I understand that I can append values to an entity reference field to a node normally with this method

$node->field_tags[] = [
    'target_id' => $my_id,
  ];

However I have a function like so

function addTag($node,$field,$id){
$node->set($field,[
    'target_id' => $id,
  ]);
}

In other words I have to anticipate any field the user supplies. Looking at the node class here

https://api.drupal.org/api/drupal/core!modules!node!src!Entity!Node.php/class/Node/8.2.x

I did discover the set function that lets me specify a field and a value but I don't believe that this would append to an array of entities in a field.

How would I append to an entity reference field to a node if the field name is supplied in a variable?

Answer 1

Yes, the class Node is a good starting point to look for an OOP way:

Click on get(), which returns a field object FieldItemList, where you can use the method appendItem():

$node->get($field)->appendItem([
  'target_id' => $id,
]);

Replace ->get() with {} and ->appendItem() with [] and you get the shorter version which @Clive mentioned in the comment:

$node->{$field}[] = $id;

This is possible because of the magic method ContentEntityBase::__get and the ArrayAccess interface the field implements. I've also dropped target_id, because you don't need this for the main property of a field.