ext_localconf.php

<?php
if (!defined('TYPO3_MODE')) {
    die('Access denied.');
}

/***************
 * Register Slots to News Extension
 */

/** @var \TYPO3\CMS\Extbase\SignalSlot\Dispatcher $signalSlotDispatcher */
$signalSlotDispatcher = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('TYPO3\\CMS\\Extbase\\SignalSlot\\Dispatcher');
$signalSlotDispatcher->connect(
    'GeorgRinger\\News\\Controller\\NewsController',
    'listAction',
    'Bk2k\\Client\\Slots\\NewsControllerSlot',
    'listActionSlot',
    TRUE
);
$signalSlotDispatcher->connect(
    'GeorgRinger\\News\\Controller\\NewsController',
    'detailAction',
    'Bk2k\\Client\\Slots\\NewsControllerSlot',
    'detailActionSlot',
    TRUE
);

NewsControllerSlot.php

<?php
namespace Bk2k\Client\Slots;

/**
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Extbase\Object\ObjectManager;
use TYPO3\CMS\Extbase\Persistence\Generic\QueryResult;
use GeorgRinger\News\Domain\Model\News;
use GeorgRinger\News\Domain\Model\Dto\NewsDemand;
use GeorgRinger\News\Domain\Repository\NewsRepository;
use Bk2k\Client\Domain\Repository\OfficeRepository;

/**
 * News Controller Slot
 */
class NewsControllerSlot
{
    /**
     * @var \TYPO3\CMS\Extbase\Object\ObjectManager
     */
    protected $objectManager;

    /**
     * @var \Bk2k\Client\Domain\Repository\OfficeRepository
     */
    protected $officeRepository;

    /**
     * @var \GeorgRinger\News\Domain\Repository\NewsRepository
     */
    protected $newsRepository;

    /**
     * @return void
     */
    public function __construct()
    {
        $this->objectManager = GeneralUtility::makeInstance(ObjectManager::class);
        $this->officeRepository = $this->objectManager->get(OfficeRepository::class);
        $this->newsRepository = $this->objectManager->get(NewsRepository::class);
    }

    /**
     * @param QueryResult $news
     * @param array $overrideDemand
     * @param array $demand
     * @return array
     */
    public function listActionSlot(QueryResult $news = null, $overrideDemand, NewsDemand $demand)
    {
        // Get tags from resultset
        $currentTags = $demand->getTags();
        $demand->setTags('');
        $filteredNewsRecords = $this->newsRepository->findDemanded($demand);
        $demand->setTags($currentTags);
        $tags = array();
        foreach ($filteredNewsRecords as $record) {
            foreach ($record->getTags() as $tag) {
                $tags[] = $tag;
            }
        }
        $uniqueTags = array_unique($tags);

        // Get headquarter
        $headquarter = $this->officeRepository->findByType(0)->getFirst();

        // Assign values
        $assignedValues = [
            'news' => $news,
            'overwriteDemand' => $overwriteDemand,
            'demand' => $demand,
            'extendedVariables' => [
                'tags' => $uniqueTags,
                'headquarter' => $headquarter
            ]
        ];
        return $assignedValues;
    }

    /**
     * @param News $newsItem
     * @param int $currentPage
     * @param array $demand
     * @return array
     */
    public function detailActionSlot(News $newsItem = null, $currentPage, NewsDemand $demand)
    {
        // Get headquarter
        $headquarter = $this->officeRepository->findByType(0)->getFirst();

        // Assign values
        $assignedValues = [
            'newsItem' => $newsItem,
            'currentPage' => $currentPage,
            'demand' => $demand,
            'extendedVariables' => [
                'headquarter' => $headquarter
            ]
        ];
        return $assignedValues;
    }
}