Re: Reconciling DataContexts

From: Aristedes Maniatis (
Date: Sat Oct 20 2007 - 19:34:49 EDT

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    On 20/10/2007, at 5:58 AM, Kevin Menard wrote:

    > 1) Overly verbose syntax. Consider:
    > a.setSomething(b);
    > versus
    > a.setSomething((BType) a.getObjectContext().localObject
    > (b.getObjectId(),
    > b));

    I have a subclass of CayenneContext in our code with this helper method:

            public Persistent localObject(Persistent po) {
                    if (po != null) {
                            if (po.getObjectContext() == this) {
                                    return po;
                            return localObject(po.getObjectId(), null);
                    return null;

    It doesn't completely solve your problem, but it does make the syntax
    slightly shorter.

    Perhaps another idea with an even simpler syntax for you is a pair of
    functions in PersistentObject:

    a.copyToContext(b) // copies to the context of b

    Personally I like the way contexts are managed in Cayenne. It is
    always clear what context an object is in and there are no hidden
    surprises. I can see what Kevin is getting at, but I think to obscure
    the copying of objects between contexts will be less clear, not more.
    Thinking about what context each object is in is part of working with
    an ORM.

    It would be great to have the context equivalent to generics: some
    indicator which tells the programmer what context an object belongs
    to and which doesn't let you (at compile time) relate objects from
    different contexts. But I can't see how such a thing is possible.

    Ari Maniatis

    Aristedes Maniatis
    phone +61 2 9660 9700
    PGP fingerprint 08 57 20 4B 80 69 59 E2 A9 BF 2D 48 C2 20 0C C8

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