Drupal Hook Node Presave acts directly on inserted/updated nodes. Bobcares, as part of our Server Management Service, responds to all Drupal inquiries, large or small.

Drupal Hook Node Presave Function

Hooks give modules access to the Drupal core. The “hooks” concept serves as the foundation for Drupal’s module system. A hook is a PHP function with the name foo_bar(), where “foo” stands for the module’s name and “bar” for the hook’s name. Also, each hook has a specific result type and a defined set of parameters.

All a module needs to do to extend Drupal is to implement a hook. Drupal determines which modules implement a hook and calls that hook in all enabled modules that implement it when it wants to allow module intervention.

Node hooks are functions for defining and modifying content types. The node operations such as create, insert, update, view, delete, etc. call several sets of hooks to let modules alter the base node operation.

While updating an existing node (calling $node->save() on an existing node), it invokes hook_node_presave(). This hook invokes node_save() before the node is saved to the database. We can find it at drupal/core/modules/node/node.api.php. It acts directly on the added/updated node.

Implementing Drupal Hook Node Presave() function

The following are the four functions to implement the hook_node_presave(), namely:

1. book_node_presave, located in drupal/core/modules/book/book.module
2. entity_crud_hook_test_node_presave, located in drupal/core/modules/system/tests/modules/entity_crud_hook_test/entity_crud_hook_test.module
3. forum_node_presave, located in drupal/core/modules/forum/forum.module
4. node_test_node_presave, located in drupal/core/modules/node/tests/modules/node_test/node_test.module

Code To Call hook_node_presave() Function

The following code will invoke the hook_node_presave():

function hook_node_presave(\Drupal\Core\Entity\EntityInterface $node) {
  if ($node->nid && $node->moderate) {

    // Reset votes when node is updated:
    $node->score = 0;
    $node->users = '';
    $node->votes = 0;
  }
}

How To Stop A Node From Saving In hook_node_presave() Function?

We must obviously throw an exception if we want to stop the node from being saved in a presave method or hook.

throw new \Exception(t('Fields are not unique!'));

Regardless of the form, Rest API, or code used, it is still a good idea to double-check this in presave to ensure that no incorrect node content is saved. If someone gets past the first level of checks in the form, then we definitely have to throw an exception.

When an exception raises, then we can catch the database connection exceptions with a custom handler.

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Conclusion

In this article, our Support team explains Drupal’s hook_node_presave function including its implementation.