add a computed field example for obtaining situation updates for banners

docroot/modules/custom/va_gov_api/src/Field/ComputedSituationUpdatesItemList.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Drupal\va_gov_api\Field;
+
+use Drupal\Core\Field\FieldItemList;
+use Drupal\Core\TypedData\ComputedItemListTrait;
+
+/**
+ * Provides a computed breadcrumbs field item list.
+ */
+class ComputedSituationUpdatesItemList extends FieldItemList {
+
+  use ComputedItemListTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function computeValue() {
+    $parent = $this->getEntity();
+    if ($parent->isNew()) {
+      return;
+    }
+
+    // Get paragraph ids from 'field_situation_updates' field.
+    $situation_updates = $parent->get('field_situation_updates')->getValue();
+    $situation_update_ids = array_column($situation_updates, 'target_id');
+
+    // Load paragraph entities.
+    $paragraphs = \Drupal::entityTypeManager()
+      ->getStorage('paragraph')
+      ->loadMultiple($situation_update_ids);
+
+    foreach ($paragraphs as $key => $paragraph) {
+      $paragraphData = [
+        'revision_id' => $paragraph->getRevisionId(),
+        'paragraph_type' => $paragraph->getType(),
+        'uuid' => $paragraph->uuid(),
+        'field_datetime_range_timezone' => $paragraph->get('field_datetime_range_timezone')
+          ->getValue()[0],
+        'field_send_email_to_subscribers' => $paragraph->get('field_send_email_to_subscribers')
+          ->getValue()[0],
+        'field_wysiwyg' => $paragraph->get('field_wysiwyg')->getValue()[0],
+      ];
+
+      $this->list[$key] = $this->createItem($key, $paragraphData);
+    }
+  }
+
+}

docroot/modules/custom/va_gov_api/va_gov_api.module

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @file
+ * Defines the hooks for va_gov_api module.
+ */
+
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+
+/**
+ * Implements hook_entity_bundle_field_info().
+ *
+ * The hook_event_dispatcher module has this hook listed as a todo.
+ *
+ * @see core_event_dispatcher.module#L26
+ */
+function va_gov_api_entity_bundle_field_info(EntityTypeInterface $entity_type, $bundle, array $base_field_definitions) {
+  if ($bundle === 'full_width_banner_alert') {
+    $base_field_definitions['computed_situations_updates'] = BaseFieldDefinition::create('map')
+      ->setName('computed_situations_updates')
+      ->setLabel(t('Computed Situation Updates'))
+      ->setComputed(TRUE)
+      ->setClass('\Drupal\va_gov_api\Field\ComputedSituationUpdatesItemList')
+      ->setCardinality(FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED);
+  }
+  return $base_field_definitions;
+}