Fetch associated entities collection from Doctrine2 repository as an array

Question

I'm starting a little project with DDD approach. I've created my domain model with Entities and ValueObjects in plain PHP. Entities have references to their associations - in my case, there is an Employee entity with collection of Teams he belongs to, and I keep them in Employee::teams property. Everything is going great, I've created mappings for those entities with associations in YAML, interfaces for repositories to be implemented in the Symfony2 and Doctrine2 layer, etc.

When I fetch Employee s from repository (with Doctrine's EntityManager::findAll() ) instead of array of Team s I receive PersistentCollection with those teams. It's built on PHP7, and Employee::getTeams() has return type of array so I'm getting the critical exception. Is there any way to convert it into array with some external listeners (Symfony layer only, to not to mess in domain files) or any other core mechanism?

Thanks.

Answer 1

You get ArrayCollection
http://www.doctrine-project.org/api/common/2.5/class-Doctrine.Common.Collections.ArrayCollection.html

It has toArray() method so you can write

/**
 * @return Team[]
 */
public function getTeams(): array
{
    return $this->teams->toArray();
}

But I prefer

/**
 * @return Team[]|ArrayCollection
 */
public function getTeams()
{
    return $this->teams;
}

If you use good IDE like PhpStorm it will understand it correctly to autocomplete it like ArrayCollection and as Team if you make foreach ($employee->getTeams() as $team) {...

ArrayCollection are more powerful than plain arrays. For example you can filter and order them and Doctrine will make optimized SQL so you don't have to load all items
http://docs.doctrine-project.org/en/latest/reference/working-with-associations.html#filtering-collections

Answer 2

Kuba,

That doesn't seem to be a DDD question but a technical question regarding PHP implementation details. However, please let me jump into your design and try to find a better solution for your domain. You are missing to model the relation between an employee and a team, let's call it employee in team. The way you did you are forcing an AR to reference another AR, saying this way that employee manages a team life cycle. This might not be the case but under a specific scenario another actor might change a status of a team and that could break the Employee invariant over the Team AR. Because of this when you make an AR to manage another AR life cycle then this dependency shouldn't be found through the repository and the root of the aggregate is in the position to now force invariant around the aggregated AR. There are still some concerns to mention, but just to keep it simple, go ahead and model the concept you are missing: EmployeeInTeam or whatever you want to call it. It references the conceptual identity of the employee and the team so you can remove it safely in a future, you can query employees in a team and teams an employee is part of. If you need frameworks or the DB to keep the consistence then you are not doing DDD. Use just objects, not the technology.

Regards, Sebastian.