Smile\ElasticsuiteCore\Api\Index\Mapping\FieldInterface::getType PHP Method

    public function getType();

 /**
  * Indicates if a field is searchable.
  *
  * @SuppressWarnings(PHPMD.UnusedPrivateMethod)
  *
  * @param FieldInterface $field Mapping field.
  *
  * @return boolean
  */
 private function isSearchableFieldCallback(FieldInterface $field)
 {
     return $field->isSearchable() && $field->getType() == FieldInterface::FIELD_TYPE_STRING;
 }