first commit for custom module

web/modules/custom/popsu_uniqdate/config/schema/popsu_uniqdate.schema.yml

@@ -0,0 +1,3 @@
+views.field.view_computed_date_unique:
+  type: views_field
+  label: 'Computed Date Unique'

web/modules/custom/popsu_uniqdate/src/Plugin/Field/FieldType/ComputedUniqDate.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace Drupal\popsu_uniqdate\Plugin\Field\FieldType;
+
+use Drupal\Core\Entity\FieldableEntityInterface;
+// use Drupal\Core\Field\EntityReferenceFieldItemList;
+// use Drupal\Core\Field\EntityReferenceFieldItemListInterface;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeItemInterface;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeFieldItemList;
+use Drupal\Core\Field\FieldItemList;
+use Drupal\Core\TypedData\TypedDataInterface;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\TypedData\ComputedItemListTrait;
+
+// https://www.drupal.org/node/2112677
+// https://www.cornel.co/article/entity-reference-computed-field-example-drupal
+// https://www.caxy.com/blog/drupal-custom-form-and-computed-fields
+
+class ComputedUniqDate extends DateTimeFieldItemList
+{
+  use ComputedItemListTrait;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(BaseFieldDefinition $definition, $name, TypedDataInterface $parent) {
+    parent::__construct($definition, $name, $parent);
+    $this->entityTypeManager = \Drupal::entityTypeManager();
+  }
+
+  /**
+   * Compute the values.
+   */
+  protected function computeValue() {
+    // $query = \Drupal::entityQuery('node')
+    $entity = $this->getEntity();
+    // $storage = \Drupal::service('entity_type.manager')->getStorage('node');
+    $dates = $entity->get('field_date')->getValue();
+    asort($dates);
+    $last_date = array_pop($dates);
+    $this->list[0] = $this->createItem(0, $last_date);
+  }
+
+}

web/modules/custom/popsu_uniqdate/src/Plugin/views/field/ViewsComputedDateUnique.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Drupal\popsu_uniqdate\Plugin\views\field;
+
+use Drupal\views\ResultRow;
+use Drupal\views\Plugin\views\field\FieldPluginBase;
+
+/**
+ * A handler to provide proper displays for profile current company.
+ *
+ * @ingroup views_field_handlers
+ *
+ * @ViewsField("views_computed_date_unique")
+ */
+class ViewsComputedDateUnique extends FieldPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render(ResultRow $values) {
+    $entity = $values->_entity;
+    $uniqdate = $entity->get('computed_date_unique')->getValue();
+    return $uniqdate[0]['value'];
+    // $dates = $entity->get('field_date')->getvalue();
+    // asort($dates);
+    // return array_pop($dates);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function query() {
+    // This function exists to override parent query function.
+    // Do nothing.
+  }
+}