Happyr\DoctrineSpecification\Filter\IsNotNull::getFilter PHP Метод

    public function getFilter(QueryBuilder $qb, $dqlAlias)
    {
        if ($this->dqlAlias !== null) {
            $dqlAlias = $this->dqlAlias;
        }
        return (string) $qb->expr()->isNotNull(sprintf('%s.%s', $dqlAlias, $this->field));
    }