public function deleteInRelation() {
    $this->requireTransaction();
    $request = $this->getRequest();

    // remove existing object from relation
    $request->setValue('role', $request->getValue('relation'));

    // delegate to AssociateController
    $subResponse = $this->executeSubAction('disassociate');

    // prevent commit
    if ($subResponse->hasErrors()) {
      $this->endTransaction(false);
    }
    $this->handleSubResponse($subResponse);
  }