Pre fill multiple paragraphs while adding node

Question

I want to prefill multiple paragraphs when user click on "add node" for specific content type. What would be a good way to do this ?

Answer 1

You can't reuse existing paragraphs, you have to create new paragraphs for each node:

$paragraph1 = Paragraph::create([
  'title' => 'Paragraph 1',
  'type' => 'paragraph_type1',
]);
$paragraph1->save();

$paragraph2 = Paragraph::create([
  'title' => 'Paragraph 2',
  'type' => 'paragraph_type2',
]);
$paragraph2->save();

$node = Node::create([
  'title' => 'Node with two paragraphs',
  'type' => 'article',
  'field_paragraph' => [$paragraph1, $paragraph2],
  ]);
$node->save();

You could place this code in a custom controller:

  public function addCustomContentType() {
    $node = $this->entityTypeManager()->getStorage('node')->create([
      'type' => 'custom_content_type',
    ]);

    // create paragraphs, don't save them yet, in case the node is not submitted

    $paragraph1 = $this->entityTypeManager()->getStorage('paragraph')->create([
      'title' => 'Paragraph 1',
      'type' => 'paragraph_type1',
       // more field data
    ]);

    $paragraph2 = $this->entityTypeManager()->getStorage('paragraph')->create([
      'title' => 'Paragraph 2',
      'type' => 'paragraph_type2',
      // more field data
    ]);

    // prefill the paragraph field in the node with the paragraphs
    $node->field_paragraph = [$paragraph1, $paragraph2];

    $form = $this->entityFormBuilder()->getForm($node);

    return $form;

Answer 2

You can hack simple fields during hook_form_alter(), but paragraphs have too complicated structure. It must be done earlier, during fresh node creation, before the form is created.

function MY_MODULE_node_create(Drupal\Core\Entity\EntityInterface $entity) {

  $bundle = $entity->bundle();
  if ($bundle != 'MY_CONTENT_TYPE') {
    return;
  }

  // you may add here additional checks
  // to make sure node creation happens
  // on node add page

  $pg = Paragraph::create([
    'type' => 'MY_PG_MACHINE_NAME',
    'field_reference' => ['target_id' => 111],
    'field_integer' => 2222,
  ]);

  // Insert here as many paragraphs as you need.
  $entity->field_paragraphs = [$pg];

}

See also: hook_entity_create()