public function attachField(IndexField $field)
    {
        // Enrich the field here, agent will probably do this.

        // Throw the SearchEvents::FIELD_ENRICH event, reset the field's value
        // with the enriched value.
//        $event = new SearchFieldEvent($this->_service, $this, $field);
//        $this->_dispatcher->dispatch(SearchEvents::FIELD_ENRICH, $event);
//        $field->setValue($event->getValue());

        $id = $field->getId();
        $this->_fields[$id] = $field;

        return $this;
    }