interface ExpressionContainerInterface

interface ExpressionContainerInterface extends ExpressionInterface, \IteratorAggregate {
  
  /**
   * Creates and adds an expression.
   *
   * @param string $plugin_id
   *   The id of the expression plugin to add.
   * @param \Drupal\rules\Context\ContextConfig $config
   *   (optional) The configuration for the specified plugin.
   *
   * @throws \Drupal\rules\Exception\InvalidExpressionException
   *   Thrown if the wrong expression is passed; e.g. if a condition expression
   *   is added to an action expression container.
   *
   * @return $this
   */
  public function addExpression($plugin_id, ContextConfig $config = NULL);
  
  /**
   * Adds an expression object.
   *
   * @param \Drupal\rules\Engine\ExpressionInterface $expression
   *   The expression object.
   *
   * @throws \Drupal\rules\Exception\InvalidExpressionException
   *   Thrown if the wrong expression is passed; e.g. if a condition expression
   *   is added to an action expression container.
   *
   * @return $this
   */
  public function addExpressionObject(ExpressionInterface $expression);
  
  /**
   * Looks up the expression by UUID in this container.
   *
   * @param string $uuid
   *   The UUID of the expression.
   *
   * @return \Drupal\rules\Engine\ExpressionInterface|false
   *   The expression object or FALSE if not expression object with that UUID
   *   could be found.
   */
  public function getExpression($uuid);
  
  /**
   * Deletes an expression identified by the specified UUID in the container.
   *
   * @param string $uuid
   *   The UUID of the expression.
   *
   * @return bool
   *   TRUE if an expression was deleted, FALSE if no expression with that UUID
   *   was found.
   */
  public function deleteExpression($uuid);
  
  /**
   * Returns an iterator for expressions in this container.
   *
   * @return \Traversable
   *   An object that may be iterated with "foreach".
   */
  public function getIterator() : \Traversable;

}