message-8.x-1.1/modules/message_example/message_example.module

<?php

/**
 * @file
 * Holds hook implementation for the Message example module.
 */

use Drupal\comment\Entity\Comment;
use Drupal\Core\Entity\ContentEntityBase;
use Drupal\message\Entity\Message;
use Drupal\node\Entity\Node;
use Drupal\user\Entity\User;

/**
 * Implements hook_node_insert().
 */
function message_example_node_insert(Node $node) {
  $message = Message::create(['template' => 'example_create_node', 'uid' => $node->get('uid')]);
  $message->set('field_node_reference', $node);
  $message->set('field_published', $node->isPublished());
  $message->save();
}

/**
 * Implements hook_comment_insert().
 */
function message_example_comment_insert(Comment $comment) {
  $message = Message::create(['template' => 'example_create_comment', 'uid' => $comment->getOwnerId()]);
  $message->set('field_comment_reference', $comment);
  $message->set('field_published', $comment->isPublished());
  $message->save();
}

/**
 * Implements hook_user_insert().
 */
function message_example_user_insert(User $account) {
  Message::create(['template' => 'example_user_register', 'uid' => $account->id()])->save();
}

/**
 * Implements hook_node_update().
 */
function message_example_node_update(Node $node) {
  if (empty($node->original)) {
    return;
  }

  message_example_update_message_status($node);
}

/**
 * Implements hook_comment_update().
 */
function message_example_comment_update(Comment $comment) {
  if (empty($comment->original)) {
    return;
  }

  message_example_update_message_status($comment);
}

/**
 * Set message entity published field when it changes in the related entity.
 *
 * @param \Drupal\Core\Entity\ContentEntityBase $entity
 *   The entity object.
 */
function message_example_update_message_status(ContentEntityBase $entity) {
  if ($entity->isPublished() == $entity->original->isPublished()) {
    return;
  }

  $query = \Drupal::entityQuery('message');

  $field = 'field_' . $entity->getEntityType()->id() . '_reference';
  $query->condition($field . '.target_id', $entity->id());

  $results = $query->accessCheck(FALSE)->execute();

  if (empty($results)) {
    return;
  }

  $messages = Message::loadMultiple($results);

  foreach ($messages as $message) {
    $message->set('field_published', $entity->isPublished());
    $message->save();
  }
}