Extra fields calculated don't work in list.php (only in card.php) in the product module

Thank you very much for your reply.

I have tried the following code but I get error 500:

(($reloadedobj = new Product($db)) && ($reloadedobj->fetch($obj->id ? $obj->id : ($obj->rowid ? $obj->rowid : $object->id)) > 0)) ? $reloadedobj->id: 3

but testing with the Societe class with the same code, it works:

(($reloadedobj = new Societe($db)) && ($reloadedobj->fetch($obj->id ? $obj->id : ($obj->rowid ? $obj->rowid : $object->id)) > 0)) ? $reloadedobj->id: 3

I don’t understand why. I am doing something wrong?
Thanks!