class.ext_update.php

<?php
use TYPO3\CMS\Core\Utility\GeneralUtility;

class ext_update
{
    /**
     * @var \TYPO3\CMS\Extbase\Object\ObjectManagerInterface
     */
    protected $objectManager;

    /**
     * frontendUserGroupRepository
     *
     * @var \TYPO3\CMS\Extbase\Domain\Repository\FrontendUserGroupRepository
     * @ inject
     */
    protected $frontendUserGroupRepository;

    /**
     * Checks whether the "UPDATE!" menu item should be
     * shown.
     *
     * @return boolean
     */
    function access() {
        # @var \TYPO3\CMS\Extbase\Validation\ValidatorResolver $validatorResolver
        $this->objectManager = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('Tx_Extbase_Object_ObjectManager');
        $this->frontendUserGroupRepository = $this->objectManager->get('\TYPO3\CMS\Extbase\Domain\Repository\FrontendUserGroupRepository');

        $querySettings = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('\TYPO3\CMS\Extbase\Persistence\Generic\Typo3QuerySettings');
        $querySettings->setRespectStoragePage(false);
#       $querySettings->setStoragePageIds(array(2,28));

        $this->frontendUserGroupRepository->setDefaultQuerySettings($querySettings);

        if (
            (0 == $this->frontendUserGroupRepository->countByTitle('GROUP1')) or
            (0 == $this->frontendUserGroupRepository->countByTitle('GROUP2'))
        )
            return true; // Update necessary
        else
            return false; // Update not necessary
    }

    /**
     * Main method that is called whenever UPDATE! was clicked.
     *
     * @return string HTML to display
     */
    function main() {
        $operation = GeneralUtility::_GP('operation');
        if ($operation) {
            // TODO: Use the value from the input field as PID
            $this->getFrontendUserGroupByName('GROUP1', 2);
            $this->getFrontendUserGroupByName('GROUP2', 2);
            $out[] = 'Update performed!';
        } else {
            $out[] = '<form action="' . GeneralUtility::linkThisScript() . '" method="post" class="container-fluid">';
            $out[] = '<label>Page UID for new Groups to be created on</label>';
            $out[] = '<input name="pid" type="number" min="1" value=""/><br/>';
            $out[] = '<button name="operation" value="UPDATE">UPDATE</button>';
            $out[] = '</form>';
        }

        return implode(LF, $out);
    }

    // Helper function
    function getFrontendUserGroupByName($frontendUserGroupTitle, $pid) {
        /** @noinspection PhpUndefinedMethodInspection */
        if (0 == $this->frontendUserGroupRepository->countByTitle('GENSER')) {
            $fe_group = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(
                '\\TYPO3\\CMS\\Extbase\\Domain\\Model\\FrontendUserGroup', $frontendUserGroupTitle
            );
            $fe_group->setPid($pid); // pageID where the group should be created
            $this->frontendUserGroupRepository->add($fe_group);
        }
        return;
    }
}