class ListDataDefinition

class ListDataDefinition extends DataDefinition implements ListDataDefinitionInterface {
    
    /**
     * The data definition of a list item.
     *
     * @var \Drupal\Core\TypedData\DataDefinitionInterface
     */
    protected $itemDefinition;
    
    /**
     * Creates a new list definition.
     *
     * @param string $item_type
     *   The data type of the list items; e.g., 'string', 'integer' or 'any'.
     *
     * @return static
     *   A new List Data Definition object.
     */
    public static function create($item_type) {
        return static::createFromItemType($item_type);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createFromDataType($type) {
        $definition = parent::createFromDataType($type);
        // If nothing else given, default to a list of 'any' items.
        $definition->itemDefinition = DataDefinition::create('any');
        return $definition;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createFromItemType($item_type) {
        return new static([], \Drupal::typedDataManager()->createDataDefinition($item_type));
    }
    
    /**
     * {@inheritdoc}
     */
    public function __construct(array $values = [], ?DataDefinitionInterface $item_definition = NULL) {
        $this->definition = $values;
        $this->itemDefinition = $item_definition;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDataType() {
        return 'list';
    }
    
    /**
     * {@inheritdoc}
     */
    public function setDataType($type) {
        if ($type != 'list') {
            throw new \LogicException('Lists must always be of data type "list".');
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getClass() {
        if (!empty($this->definition['class'])) {
            return $this->definition['class'];
        }
        // If a list definition is used but no class has been specified, derive the
        // default list class from the item type.
        $item_type_definition = \Drupal::typedDataManager()->getDefinition($this->getItemDefinition()
            ->getDataType());
        if (!$item_type_definition) {
            throw new \LogicException("An invalid data type '{$this->getItemDefinition()->getDataType()}' has been specified for list items");
        }
        return $item_type_definition['list_class'];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getItemDefinition() {
        return $this->itemDefinition;
    }
    
    /**
     * Sets the item definition.
     *
     * @param \Drupal\Core\TypedData\DataDefinitionInterface $definition
     *   A list item's data definition.
     *
     * @return $this
     */
    public function setItemDefinition(DataDefinitionInterface $definition) {
        $this->itemDefinition = $definition;
        return $this;
    }
    
    /**
     * Magic method: Implements a deep clone.
     */
    public function __clone() {
        // Ensure the itemDefinition property is actually cloned by overwriting the
        // original reference.
        $this->itemDefinition = clone $this->itemDefinition;
    }

}