Filtering for seleted categories and subcategories in extbase TYPO3 frontend plugin - typo3

Question

I am using TYPO3 8.7.
I have got an extension which allows to list events. In the list plugin settings the redactor selects the categories. He wants that all events which have the selected category or a subcategory of it assigned are show in the frontend.
I have been reading the documentation on docs.typo3.org and have been looking at the class CategoryCollection. As far as I understand, this class helps me to get the keywords for a certain record, but does not help to select records by a keyword.
I would like to filter also for subcategories because it makes the handling of the extension much easier. Let's imagine the following event categories:
course of studies
master's degree
bachaelor's degree
training
internal training
external training
The backend editor wants to have the choice to display either e.g. internal trainings or all trainings, without activating the parent categories on every event explicitly.
What is the correct way to filter for categories and its subcategories in an extbase repository to display a list of records in the frontend?
Do I have to implement the logic manually to filter for categories and subcategories?

Answer 1

My solution looks like this:
<?php
namespace Snowflake\Events\Domain\Repository;
/***************************************************************
* Copyright notice
*
* (c) 2018 snowflake productions gmbh <support#snowflake.ch>
* All rights reserved
*
* This script is part of the TYPO3 project. The TYPO3 project is
* free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* The GNU General Public License can be found at
* http://www.gnu.org/copyleft/gpl.html.
*
* This script is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* This copyright notice MUST APPEAR in all copies of the script!
***************************************************************/
use TYPO3\CMS\Core\Database\ConnectionPool;
use TYPO3\CMS\Core\Database\Query\QueryBuilder;
use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Extbase\Persistence\Repository;
class EventRepository extends Repository {
/**
* #param $categories
* #return array|\TYPO3\CMS\Extbase\Persistence\QueryResultInterface
* #throws \TYPO3\CMS\Extbase\Persistence\Exception\InvalidQueryException
*/
public function findByCategoryFilter($categories)
{
$categories = array_map('intval', explode(',', $categories));
$categories = $this->expandCategories($categories);
$uids = $this->getUidsByCategories($categories);
if (count($uids) == 0)
return array();
$query = $this->createQuery();
$query->matching(
$query->in('uid', $uids)
);
return $query->execute(true);
}
/**
* Return the categories and all subcategories (recursive)
*
* #param $categories
* #return array
*/
private function expandCategories($categories)
{
// get all categories from database
/** #var QueryBuilder $queryBuilder */
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)
->getQueryBuilderForTable('sys_category');
$queryBuilder->getRestrictions()->removeAll();
$queryBuilder
->select('uid', 'parent')
->from('sys_category');
$allCategoriesFromDatabase = $queryBuilder->execute()->fetchAll();
// index the categories by parent
$categoriesByParent = array();
foreach($allCategoriesFromDatabase as $categoryFromDatabase) {
$categoriesByParent[(int)$categoryFromDatabase['parent']][] = (int)$categoryFromDatabase['uid'];
}
// expand the categories to all subcategories
$categoriesToExpand = $categories;
$expandedCategories = $categories;
while(count($categoriesToExpand) > 0) {
$currentSubCategories = array();
foreach($categoriesToExpand as $category) {
foreach ($categoriesByParent[$category] as $subCategory) {
$currentSubCategories[] = $subCategory;
}
}
$categoriesToExpand = array_diff($currentSubCategories, $expandedCategories);
$expandedCategories = array_unique(array_merge($expandedCategories, $currentSubCategories));
}
return $expandedCategories;
}
/**
* This is a workaround because
*
* $query = $this->createQuery();
* $query->matching(
* $query->contains('category', $categories)
* );
* return $query->execute(true);
*
* generate a useless SQL query (equals instead of in, see first WHERE condition in subquery)
*
* SELECT `tx_events_domain_model_event`.*
* FROM `tx_events_domain_model_event` `tx_events_domain_model_event`
* WHERE (`tx_events_domain_model_event`.`uid` IN
* (SELECT `uid_foreign`
* FROM `sys_category_record_mm`
* WHERE (`uid_local` = '1,3,5,4,6')
* AND ((`sys_category_record_mm`.`tablenames` = 'tx_events_domain_model_event')
* AND (`sys_category_record_mm`.`fieldname` = 'category'))))
* AND (`tx_events_domain_model_event`.`sys_language_uid` IN (0, -1))
* AND (`tx_events_domain_model_event`.`pid` = 161)
* AND ((`tx_events_domain_model_event`.`deleted` = 0)
* AND (`tx_events_domain_model_event`.`hidden` = 0)
* AND (`tx_events_domain_model_event`.`starttime` <= 1516715340)
* AND (
* (`tx_events_domain_model_event`.`endtime` = 0)
* OR (`tx_events_domain_model_event`.`endtime` > 1516715340)))
*
* #param $categories
* #return array
*/
private function getUidsByCategories($categories) {
$result = array();
/** #var QueryBuilder $queryBuilder */
$queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)
->getQueryBuilderForTable('sys_category_record_mm');
$queryBuilder->getRestrictions()->removeAll();
$queryBuilder
->select('uid_foreign')
->from('sys_category_record_mm')
->where(
$queryBuilder->expr()->andX(
$queryBuilder->expr()->in('uid_local', $categories),
$queryBuilder->expr()->eq('tablenames', '\'tx_events_domain_model_event\''),
$queryBuilder->expr()->eq('fieldname', '\'category\'')
)
);
$records = $queryBuilder->execute()->fetchAll();
foreach($records as $record) {
$result[] = $record['uid_foreign'];
}
return $result;
}
}