Drupal Module Development & API Flashcards

Which Drupal hook allows a module to alter an existing form before it is rendered?

Answer: hook_form_alter()

hook_form_alter() receives the form array by reference and lets any module modify fields, validators, submit handlers, or structure of any form.

In Drupal, what is the purpose of the #cache property in a render array?

Answer: Define cache tags, contexts, and max-age for granular caching

The #cache property with tags, contexts, and max-age keys lets Drupal cache render array output at the right granularity and invalidate it precisely.

What Drupal API is used to execute a database query that loads multiple nodes matching specific field values?

Answer: EntityQuery via \Drupal::entityQuery()

EntityQuery (via \Drupal::entityQuery() or injected entity type manager) provides a safe, entity-aware query builder that respects access control.

What is a Drupal 'Event Subscriber' and which Symfony component does it leverage?

Answer: A class that listens to dispatched events using Symfony EventDispatcher

Event Subscribers implement EventSubscriberInterface from Symfony's EventDispatcher component and react to events like KernelEvents::REQUEST without using hooks.

In Drupal's Plugin API, what is the role of the @annotation on a plugin class?

Answer: Registers the plugin with Drupal's plugin manager at discovery time

Drupal uses Doctrine annotations (like @Block, @Field, @ViewsField) in class docblocks to auto-discover and register plugins without manual registry files.

Which Drush command regenerates Drupal's autoloader and clears all caches after adding a new module?

Answer: Both drush cr and drush cache:rebuild (they are aliases)

'drush cr' and 'drush cache:rebuild' are aliases for the same command that rebuilds all Drupal caches including the service container and autoloader.