Aggregate Root references other aggregate roots

Question

I\'m currently working a lot with DDD, and I\'m facing a problem when loading/operating on aggregate roots from other aggregate roots.

For each aggregate root in my

Answer 1

I've been in this situation myself and came to a conclusion that it's too much of a head ache to make child aggregates work in an elegant way. Instead, I'd consider whether you actually need to reference the second aggregate as child of the first. It makes life much easier if you just keep a reference of the aggregate's ID rather than the actual aggregate itself. Then, if there is domain logic that involves both aggregates this can be extracted to a domain service and look something like this:

public class DomainService
{
    private readonly IAggregate1Repository _aggregate1Repository;
    private readonly IAggregate2Repository _aggregate2Repository;

    public void DoSomething(Guid aggregateID)
    {
        Aggregate1 agg1 = _aggregate1Repository.Get(aggregateID);
        Aggregate2 agg2 = _aggregate2Repository.Get(agg1.Aggregate2ID);

        agg1.DoSomething(agg2);
    }
}

EDIT:

I REALLY recommend these articles on the subject: https://vaughnvernon.co/?p=838

Answer 2

Perhaps the AggregateRoot1 repository could call AggregateRoot2 repository when it's constructing the the AggregateRoot1 entity.

I don't think this invalidates ffffd since the repositories are still in charge of getting/creating their own entities.

Answer 3

This approach have some issues. first, you should have one repository to each aggregate and its done. having one repository that calls another one is a break on this rule. second, a good practice about aggregate relationship is that one root aggregate should communicate with another root aggregate by its id, not having its reference. doing so, you keep each aggregate independent of another aggregate. keep reference in root aggregate only of the classes that compose the same aggregate.