Aqueduct ORM multiple nested joins

Question

I am using Aqueudct ORM with data models like so:

    A
    |    (one-one)
    B
  / | \  (all many-one)
 C  C  C

and my Tables look like so:

class _A {
  B b;
}

class _B {
  @Relate(#c1Ref)
  C c1;
  @Relate(#c2Ref)
  C c2;
  @Relate(#c3Ref)
  C c3;
}

class _C {
  ManagedSet<B> c1Ref;
  ManagedSet<B> c2Ref;
  ManagedSet<B> c3Ref;
}

I want to write a query to fetch big fat A, but I can't figure it out.

So far, I have:

final query = Query<A>(context)
  ..join(object: (a) => a.b)
   //Note the non-cascading dot
  .join(object: (b) => b.c1);

This gives me A with B but with only c1. How do I write a query such that I get c2 and c3 as well?

score 3 · Accepted Answer · answered Sep 01 '19 at 20:21

The join method returns a new query object. This query is a child of the original query, and controls the parameters of the query on the joined table. That is, you can apply a where condition to the new query object that applies to the joined table. In your case, you want to assign the new query object to a variable first and then set up each join. I’m on mobile right now so this may not come out great:

  final query = Query<A>(context);
  final bQuery = query.join(object: (a) => a.b)
       ..join(object: (b) => b.c1)
       ..join(object: ( b) => b.c2)
        ..join(object: (b) => b.c3);

Note that you didn’t really have put this on into a variable here, but I did to illustrate the point. You would execute ‘query’ here, not ‘bQuery’.

Y

Yes this works, thanks! My issue was that I also have a `.where` on the `Query`, and I couldn't add the joins before or after it. I did not know that `.join` modifies the query itself; I thought it was always returning a new query object. Thanks a lot! — Vedavyas Bhat, Sep 02 '19 at 13:54
Great! And yes, the parent query keeps a reference to the newly created query object. — Joe Conway, Sep 02 '19 at 14:24

Aqueduct ORM multiple nested joins

1 Answers1