I have an entity called Entity Product. And this entity has a form, if you change the Title field in this form, Drupal will automatically save the new value of this field in the appropriate table in the database, but in addition, I also save the change of the Title field in the form to another database table product_product by creating a _custom_product_save_title function. It is necessary. And this function is called in the hook_ENTITY_TYPE_update() which tracks changes in Entity Product.

I need to add a check to see if the title is saved and if other fields are not saved. Please tell me what such a check should look like and where exactly should it be in the code?

function _custom_product_save_title($custom_product_id, $entity_product_title) {    if (isset($fields['url']) && $fields['url'] == '') {     if (isset($fields['name'])) {       $fields['url'] = strtolower(str_replace(' ', '-', $fields['name']));     }   }   $id = $form_state->getValue('cid');   if (!empty($form_state->getValue('cid'))) {     $query = $this->connection->update($this->getTableName())       ->condition('cid', $form_state->getValue('cid'));   }   else {     $query = $this->connection->insert($this->getTableName());   }   $result = $query     ->fields($fields)     ->execute();   if (!$id) {     $id = $result;   }     Cache::invalidateTags([     "product:" . $form_state->getValue('cid'),   ]);    Cache::invalidateTags([     "product:$custom_product_id",   ]);    if (!$custom_product_id) {     Cache::invalidateTags([       "product_list",     ]);   }  }  /**  * Implements hook_ENTITY_TYPE_update().  */ function product_admin_node_update(DrupalCoreEntityEntityInterface $entity) {   if ($entity->bundle() == 'product') {     $custom_product_id = $entity->get('field_product_cid')->value;     $entity_product_title = $entity->getTitle();     _custom_product_save_title($custom_product_id, $entity_product_title);   } }  

After debugging the code using xdebug, I see the following structure of what comes in the standard argument $entity of the hook:

$entity   fields     field_product_cid     field_second     .....     title       x-default         list           0             values               value = “My title”