TYPO3 - Render usergroups of a logged in user as a comma separated string in fluid

Question

How can I render the usergroups of a logged in user as a comma separated string in fluid? So I would like to the this:

3,9

Controller:

$user = $this->userRepository->findByUid($GLOBALS['TSFE']->fe_user->user['uid']);
$this->view->assign('user', $user);

List.html

<f:layout name="Default" />
<f:section name="main"> 

    <f:debug>{user}</f:debug>   

</f:section>    

Extbase Variable Dump

TYPO3\CMS\Extbase\Domain\Model\FrontendUser prototype persistent entity (uid=4, pid=25)
   username => protected 'testuser01' (10 chars)
   password => protected 'sdfgsdxxcxsdf' (34 chars)
   usergroup => protectedTYPO3\CMS\Extbase\Persistence\ObjectStorage prototype object (2 items)
      00000000sdffsa => TYPO3\CMS\Extbase\Domain\Model\FrontendUserGroup prototype persistent entity (uid=3, pid=25)
         title => protected 'Group 1' (7 chars)
         uid => protected 3 (integer)
         ...
      0000000werwerw => TYPO3\CMS\Extbase\Domain\Model\FrontendUserGroup prototype persistent entity (uid=9, pid=25)
         title => protected 'Group 2' (7 chars)
         ...
         uid => protected 9 (integer)
         ...
   name => protected 'Test User 01' (12 chars)
   firstName => protected 'Test' (4 chars)
   ...

Answer 1

You can do this using f:for viewhelper like below.

<f:for each="{user.usergroup}" as="group" iteration="iterator">
    {group.uid}
    <f:if condition="{iterator.isLast}">
        <f:then> </f:then>
        <f:else>,</f:else>
    </f:if>
</f:for>