/** * Resolves an alias into a Version. * * @param string $alias * * @param Collection $collection * @return VersionInterface|null */ protected function doResolve($alias, Collection $collection) { if (!$collection instanceof Sortable) { return null; } $result = null; switch (strtolower($alias)) { case self::LAST: case self::LATEST: $result = $collection->last(); break; case self::FIRST: case self::EARLIEST: $result = $collection->first(); break; default: } return $result; }