Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/views/src/FieldAPIHandlerTrait.php

@@ -0,0 +1,79 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\views\FieldAPIHandlerTrait.
+ */
+
+namespace Drupal\views;
+
+use Drupal\Core\Field\BaseFieldDefinition;
+
+/**
+ * A trait containing helper methods for field definitions.
+ */
+trait FieldAPIHandlerTrait {
+
+  /**
+   * The field definition.
+   *
+   * @var \Drupal\Core\Field\FieldDefinitionInterface
+   */
+  protected $fieldDefinition;
+
+  /**
+   * The field storage definition.
+   *
+   * @var \Drupal\field\FieldStorageConfigInterface
+   */
+  protected $fieldStorageDefinition;
+
+  /**
+   * Gets the field definition.
+   *
+   * A View works on an entity type across bundles, and thus only has access to
+   * field storage definitions. In order to be able to use widgets and
+   * formatters, we create a generic field definition out of that storage
+   * definition.
+   *
+   * @see BaseFieldDefinition::createFromFieldStorageDefinition()
+   *
+   * @return \Drupal\Core\Field\FieldDefinitionInterface
+   *   The field definition used by this handler.
+   */
+  protected function getFieldDefinition() {
+    if (!$this->fieldDefinition) {
+      $field_storage_config = $this->getFieldStorageDefinition();
+      $this->fieldDefinition = BaseFieldDefinition::createFromFieldStorageDefinition($field_storage_config);
+    }
+    return $this->fieldDefinition;
+  }
+
+  /**
+   * Gets the field storage configuration.
+   *
+   * @return \Drupal\field\FieldStorageConfigInterface
+   *   The field storage definition used by this handler
+   */
+  protected function getFieldStorageDefinition() {
+    if (!$this->fieldStorageDefinition) {
+      $field_storage_definitions = $this->getEntityManager()->getFieldStorageDefinitions($this->definition['entity_type']);
+      $this->fieldStorageDefinition = $field_storage_definitions[$this->definition['field_name']];
+    }
+    return $this->fieldStorageDefinition;
+  }
+
+  /**
+   * Returns the entity manager.
+   *
+   * @return \Drupal\Core\Entity\EntityManagerInterface
+   *   The entity manager service.
+   */
+  protected function getEntityManager() {
+    if (!isset($this->entityManager)) {
+      $this->entityManager = \Drupal::entityManager();
+    }
+    return $this->entityManager;
+  }
+
+}