Re: using axiom.dependency for powerups in queries

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* Robert Gravina <[email protected]> [2008-03-11 19:33:05 +0900]:

> Great, thanks! That works, but I'm really thinking of the case where I'd=
=20
> be using store.query to return a list of people... I just used findFirst=
=20
> in this example because there was only one. E.g., for many Person:
>
>     for person in s.query(Contractor, Contractor.rate =3D=3D Decimal("40"=
)):
>         p =3D dependency.installedOn(person)
>
> works, as does:
>
>     people =3D [dependency.installedOn(person) for person in s.query=20
> (Contractor, Contractor.rate =3D=3D Decimal("40"))]
>
> but is there a way to get the query to return Person instead of =20
> Contractor?

Theoretically you could write a query that joins on Person, Contractor,
and _DependencyConnector; but using private names is a bad idea, the
query probably wouldn't be much more efficient, and it would be a lot
harder to understand.

Perhaps I should add that using powerups for your Contractor / Person
relationship seems quite artificial; I would just add an attribute to
Contractor:

    person =3D reference(reftype=3DContractor)

and then write queries like:

s.query(Person, AND(Person.storeID =3D=3D Contractor.person,
                    Contractor.rate =3D=3D Decimal("40")))

I think the main uses of powerups are where the powerup interface is the
primary concern; either for adaptation of an item, or because you have
multiple items of different types, but providing the same interface, and
you want to treat them as a group.
--=20
mithrandi, i Ainil en-Balandor, a faer Ambar

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