public function getActiveServices()
    {
        $active = array();
        foreach ($this->getExtensions() as $handle) {
            $service = $this->getService($handle);
            $version = $service->getDetector()->detect();
            if ($version !== null) {
                $active[] = $this->getService($handle, $version);
            }
        }

        return $active;
    }