Symfony 5 : setting a property based on a parent property value - symfony

Question

In Symfony 5, let's say we have 3 entities linked like this :
Foo is an entity that have Bar as child. Foo as one property called fooProperty.
Bar have Foo as parent, and Baz as child
Baz have Bar as parent, of course. Baz have one property called bazProperty.
Let's say that the value of bazProperty is dependent of the value of the value of fooProperty. My first idea was to refer to foo entity inside the baz entity class :
function setBazProperty($value) {
if ($this->getBar()->getFoo()->getFooProperty > 0) {
$this->bazProperty = $value;
} else {
$this->bazProperty = 0;
}
}
But this occur many sql queries, as Doctrine will ask first to get Bar entity, then Foo entity.
So I imagine to access to Foo entity through an unique query managed in a repository class.
But, because of the separation of concern, I wouldn't inject the repository in the Baz entity, but I would use a service instead.
So I've created a BazService with two arguments in the constructor :
public function __construct(Baz $baz, BazRepository $bazRepository)
{
$this->baz = $baz;
$this->bazRepository= $bazRepository;
}
In this service, I've also added a method fetching Foo entity :
public function getFoo()
{
return $this->bazRepository->getFoo($this->baz);
}
And last, in a controller, now I would like to get Foo entity :
$bazService = new BazService($baz);
$foo = $bazService->getFoo();
Here are my questions :
I'm not able to initialize bazService in the controller. The constructor ask for 2 argmuments (the entity and the repository) and I would like only to provide the entity and to inject automatically the repository class.
I've tried to add it in serices.yaml without success (probably because I didn't instantiate bazService in the constructor of my controller) :
App\Service\BazService:
arguments:
$bazRepository: App\Repository\BazRepository
Is there any other solution ? How I can inject the entity class differently in the service class ?
Using a service when setting a property is too complex is the recommended solution ? Some article (here, here and here) recommend to use a service when the method inside entity class become more complex and require external entity or repositories. But maybe there's a lighter solution...

Answer 1

Separation of concerns is IMHO the right argument to look at. There are some approaches to go for, that depend largely on how you retrieve the entity. However, in my opinion, the concern of an entity is NOT to fetch some other entities data from the database, it is the repository's or maybe the controller's concern. So let's see how to do that ...
One way is to automatically retrieve the parent entity / entities. Depending on your use case, you could do that in general (via fetch="EAGER" - see: #ManyToOne / #OneToOne), otherwise you could implement a special repository function, that fetches the additional entities. If your entities always only have at most one parent each, this can absolutely reduce the number of queries from 3 to 1, since the parent and parent of parent entities can be retrieved simultaneously.
// in BazRepository
public function getWithParents($id) {
$qb = $this->createQueryBuilder('baz');
$qb->leftJoin('baz.bar', 'bar')
->addSelect('bar')
->leftJoin('bar.foo', 'foo')
->addSelect('foo')
->where('baz.id = :id')
->setParameter('id', $id);
return $qb->getQuery()->getOneOrNullResult();
}
if the child entity accesses the parent entity, it should just use the entity from cache and avoid a second query (source: https://symfonycasts.com/screencast/doctrine-relations/join-n-plus-one)
If having the entities is already "too much", you can slightly cheat by (again) creating a custom repository method that not only fetches the Baz entity, but also the Foo.fooProperty value and sets it for a virtual/temporary property on the Baz entity.
// in BazRepository
public function getWithFooProperty(int $id) {
$qb = $this->createQueryBuilder('baz');
$qb->leftJoin('baz.bar', 'bar')
->lefTJoin('bar.foo', 'foo')
->select('foo.fooProperty as fooProperty')
->where('baz.id = :id')
->setParameter('id', $id);
$result = $qb->getQuery()->getResult(); // should be an array with an array with two keys, but I might be wrong
if(count($result) == 0) {
return null;
}
$baz = $row[0][0];
$baz->fooProperty = $row[0][1];
return $baz;
}
(Disclaimer: please check the $result here, to see if the accesses are correct)
you now could access it in Baz:
function getFooProperty() {
if(isset($this->fooProperty)) {
return $this->fooProperty;
} else {
// fallback, in case entity was fetched by another repository method
return $this->getBar()->getFoo()->getFooProperty();
}
}