lib/Query/Common/CriterionVisitor/Field.php
protected function mapSearchFieldValue($value, FieldType $searchFieldType = null)
    {
        if (null === $searchFieldType) {
            return $value;
        }

        $searchField = new SearchField('field', $value, $searchFieldType);
        $value = (array)$this->fieldValueMapper->map($searchField);

        return current($value);
    }
protected function mapSearchFieldValue($value, FieldType $searchFieldType = null)
    {
        if (null === $searchFieldType) {
            return $value;
        }

        $searchField = new SearchField('field', $value, $searchFieldType);
        $value = (array)$this->fieldValueMapper->map($searchField);

        return current($value);
    }
Map search field value to solr value using FieldValueMapper.

@param mixed $value
@param \eZ\Publish\SPI\Search\FieldType $searchFieldType

@return mixed