[TYPO3-mvc] How to get the PID of a model?

[Alexander Schnitzler]

Hey Guys,

I am extending the Extbase FrontendUser and due to some unimportant 
reason I would like to implement a getter for the PID but that does not 
work. I always get null.

I found a thread in which Jochen explains that this only works with an 
extra TCA-Mapping:

'pid' => array(
	'exclude' => 1,
	'config'  => array(
		'type' => 'passthrough'
	)
),

Now i extended the TCA like that in the ext_tables.php:

t3lib_div::loadTCA('fe_users');
$TCA['fe_users'] = array (
     'columns' => array (
         'pid' =>  array(
             'exclude' =>  1,
             'config'  =>  array(
                 'type' =>  'passthrough'
             )
         )
     )
);

If I have a look at the TCA in the Backend that works but my property 
PID is still null. So what am I doing wrong?

Alexander Schnitzler