private function invokeListener($listener, $event)
    {
        if (is_array($listener))
        {
            list($listenerClass, $method) = $listener;

            $listenerInstance = $this->objectManager->get($listenerClass);
            $listenerInstance->{$method}($event);
        }
        else
        {
            call_user_func($listener, $event);
        }
    }