class EntityWrapper

Context.php in drupal/core/lib/Drupal/Core/Plugin/Context/Context.php

Contains \Drupal\Core\Plugin\Context\Context.

class EntityWrapper extends TypedData implements IteratorAggregate, ComplexDataInterface {

  /**
   * The referenced entity type.
   *
   * @var string
   */
  protected $entityType;

  /**
   * The entity ID if no 'id source' is used.
   *
   * @var string
   */
  protected $id;

  /**
   * If set, a new entity to create and reference.
   *
   * @var \Drupal\Core\Entity\EntityInterface
   */
  protected $newEntity;

  /**
   * Overrides TypedData::__construct().
   */
  public function __construct(array $definition, $name = NULL, TypedDataInterface $parent = NULL) {
    parent::__construct($definition, $name, $parent);
    $this->entityType = isset($this->definition['constraints']['EntityType']) ? $this->definition['constraints']['EntityType'] : NULL;
  }

  /**
   * Overrides \Drupal\Core\TypedData\TypedData::getValue().
   */
  public function getValue() {
    if (isset($this->newEntity)) {
      return $this->newEntity;
    }
    if (!empty($this->definition['settings']['id source'])) {
      $this->id = $this->parent
        ->__get($this->definition['settings']['id source']);
    }
    return $this->id ? entity_load($this->entityType, $this->id) : NULL;
  }

  /**
   * Overrides \Drupal\Core\TypedData\TypedData::setValue().
   *
   * Both the entity ID and the entity object may be passed as value.
   */
  public function setValue($value, $notify = TRUE) {

    // Support passing in the entity object. If it's not yet saved we have
    // to store the whole entity such that it could be saved later on.
    if ($value instanceof EntityInterface && $value
      ->isNew()) {
      $this->newEntity = $value;
      $this->entityType = $value
        ->entityType();
      $value = 0;
    }
    elseif ($value instanceof EntityInterface) {
      $this->entityType = $value
        ->entityType();
      $value = $value
        ->id();
      unset($this->newEntity);
    }
    elseif (isset($value) && !(is_scalar($value) && !empty($this->definition['constraints']['EntityType']))) {
      throw new InvalidArgumentException('Value is not a valid entity.');
    }

    // Update the 'id source' property, if given.
    if (!empty($this->definition['settings']['id source'])) {
      $this->parent
        ->__set($this->definition['settings']['id source'], $value, $notify);
    }
    else {

      // Notify the parent of any changes to be made.
      if ($notify && isset($this->parent)) {
        $this->parent
          ->onChange($this->name);
      }
      $this->id = $value;
    }
  }

  /**
   * Overrides \Drupal\Core\TypedData\TypedData::getString().
   */
  public function getString() {
    if ($entity = $this
      ->getValue()) {
      return $entity
        ->label();
    }
    return '';
  }

  /**
   * Implements \IteratorAggregate::getIterator().
   */
  public function getIterator() {
    if ($entity = $this
      ->getValue()) {
      return $entity
        ->getIterator();
    }
    return new ArrayIterator(array());
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::get().
   */
  public function get($property_name) {

    // @todo: Allow navigating through the tree without data as well.
    if ($entity = $this
      ->getValue()) {
      return $entity
        ->get($property_name);
    }
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::set().
   */
  public function set($property_name, $value, $notify = TRUE) {
    $this
      ->get($property_name)
      ->setValue($value, FALSE);
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getProperties().
   */
  public function getProperties($include_computed = FALSE) {
    if ($entity = $this
      ->getValue()) {
      return $entity
        ->getProperties($include_computed);
    }
    return array();
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinition().
   */
  public function getPropertyDefinition($name) {
    $definitions = $this
      ->getPropertyDefinitions();
    if (isset($definitions[$name])) {
      return $definitions[$name];
    }
    else {
      return FALSE;
    }
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
   */
  public function getPropertyDefinitions() {

    // @todo: Support getting definitions if multiple bundles are specified.
    return \Drupal::entityManager()
      ->getStorageController($this->entityType)
      ->getFieldDefinitions($this->definition['constraints']);
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyValues().
   */
  public function getPropertyValues() {
    if ($entity = $this
      ->getValue()) {
      return $entity
        ->getPropertyValues();
    }
    return array();
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::setPropertyValues().
   */
  public function setPropertyValues($values) {
    if ($entity = $this
      ->getValue()) {
      $entity
        ->setPropertyValues($values);
    }
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::isEmpty().
   */
  public function isEmpty() {
    return !$this
      ->getValue();
  }

  /**
   * Implements \Drupal\Core\TypedData\ComplexDataInterface::onChange().
   */
  public function onChange($property_name) {

    // Notify the parent of changes.
    if (isset($this->parent)) {
      $this->parent
        ->onChange($this->name);
    }
  }

}