Extbase—get all items within a given category - typo3

Question

I am quite new to Typo3 and Extbase so I am really kind of lost right now… We have a category tree like that:
+ root
++ chairs
++ wooden chairs
+ plastic chairs (2)
+ generic chairs (0)
+ broken chairs
++ slightly broken chairs (3)
+ heavily broken chairs (1)
+ chairs that kill (10)
And we have a dataset (custom extension and database table etc.) and each record can be assigned to a category, what is a built in functionality of typo3. We also have a Repository class which implements a findByCategory() method.
We would like to list all records from the custom table, which are member of a given category. So in case of the example above, findByCategory('broken chairs') should yield 14 items and findByCategory('chairs') 16.
Is there any Helper/Utility Class we can use to obtain all categories from a given parent category?

Answer 1

I think you have to extend the CategoryRepository and implement your own method. The method could look like this :
/**
* Finds categories based on their parents, possibly taking categories2skip into account
*
* #param integer $parent
* #param array $categories2skip
*
* #return object
*/
public function findByParent($parent, $categories2skip = array()) {
$query = $this->createQuery();
$constraints = array();
$constraints[] = $query->equals('parent', $parent);
if (count($categories2skip) > 0) {
$constraints[] = $query->logicalNot($query->in('uid', $categories2skip));
}
$query->matching(
$query->logicalAnd($constraints)
);
$result = $query->execute();
return $result;
}