Expanded class hierarchy of AttributeString in Drupal 9
- class \Drupal\Core\Template\AttributeValueBase
- class \Drupal\Core\Template\AttributeArray implements \Drupal\Core\Template\ArrayAccess, \Drupal\Core\Template\IteratorAggregate
- class \Drupal\Core\Template\AttributeBoolean
- class \Drupal\Core\Template\AttributeString