typo3 - How to update 1:1 relations in Extbase -

i have 2 models below

class communication extends \typo3\cms\extbase\domainobject\abstractentity {     /**      * @var filter      */     protected $filter; }  class filter extends \typo3\cms\extbase\domainobject\abstractentity {     /**      * @var \typo3\cms\extbase\persistence\objectstorage<\typo3\cms\extbase\domain\model\frontendusergroup>      */     protected $usergroup; } 

template below

<f:form class="form-horizontal" name="communication" action="update" object="{communication}">     <div class="form-group">         <label class="col-xs-3 col-md-2 control-label" for="bodytext">{f:translate(key: 'text.usergroup')}</label>         <div class="col-xs-9 col-md-10">             <f:for each="{usergroups}" as="group">                 <label class="checkbox-inline">                     <f:form.checkbox property="filter.usergroup" value="{group.uid}" /> {group.title}                 </label>             </f:for>         </div>     </div>     <div class="form-group">         <div class="col-xs-9 col-md-10 col-xs-offset-3 col-md-offset-2">             <button type="submit" class="btn btn-primary">{f:translate(key: 'button.update')}</button>         </div>     </div> </f:form> 

when try update communication $this->communicationrepository->update($communication), creates new filter rather updating own. why this?

this because there no relation filter there. keeping filter need id has. found out works __identity field:

edit: better wrap field if condition in case there no filter set

<f:if condition="{communication.filter.uid}">     <f:form.hidden name="communication[filter][__identity]" value="{communication.filter.uid}" /> </f:if> 

not sure, possible works uid property field:

<f:form.hidden property="filter.uid" />