[TYPO3-mvc] How and where should I sort my data?

[Oliver Salzburg]

I'm trying to get my feet wet with extbase/fluid development and am
kind of confused about where to properly sort my collected data.

I only have 2 entities that are relevant: Item and Category.
Every Item should only be in a single Category.

So far so good, everything is working pretty great. I get my list of
Items in the frontend, but not sorted as I want them.
So I added the following snippet to my ItemRepository:

  public function findThings() {
    $query = $this->createQuery();
    $query->setOrderings(
      array(
        "category" =>
Tx_Extbase_Persistence_QueryInterface::ORDER_DESCENDING
      )
    );

    return $query->execute();
  }

Great, now my Items are sorted the the ID of the Category.
But what I *really* want is to sort them based on the *Name* of my
Category.

I tried several approaches that seemed logical to me but either
resulted in error messages or seemed to have no effect.

How is this generally solved?

Cheers
Oliver