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;

}