src/Zf2Forum/Model/Visit/VisitHydrator.php
public function extract($object)
    {
        if (!$object instanceof VisitInterface) {
            throw new Exception\InvalidArgumentException(
                '$object must be an instance of Zf2Forum\Model\Visit\VisitInterface'
            );
        }
        $data = parent::extract($object);

        $thread = $object->getThread();
        $data['thread_id'] = (int)$thread->getThreadId();
        unset($data['thread']);
        $data['visit_time'] = $data['visit_time']->format('Y-m-d H:i:s');
        return $data;
    }
public function extract($object)
    {
        if (!$object instanceof VisitInterface) {
            throw new Exception\InvalidArgumentException(
                '$object must be an instance of Zf2Forum\Model\Visit\VisitInterface'
            );
        }
        $data = parent::extract($object);

        $thread = $object->getThread();
        $data['thread_id'] = (int)$thread->getThreadId();
        unset($data['thread']);
        $data['visit_time'] = $data['visit_time']->format('Y-m-d H:i:s');
        return $data;
    }
extract

@param unknown_type $object
@throws Exception\InvalidArgumentException
@return unknown