QtDBus and user types problem

Sebastian Trüg strueg at mandriva.com
Sat Nov 4 02:09:00 PST 2006

I see.
thanks a lot for the help.
So there is no generic way to it. Ok. One last question although I think the 
answer is no: Would it be possible to get the raw data from the QDBusArgument 
to have it demarshalled elsewhere?


On Saturday 04 November 2006 11:27, Thiago Macieira wrote:
> Sebastian Trüg wrote:
> >Now when I use  QDBusInterface::callWithArgumentList to retrieve a
> > return value of type MyUserType I get a QList<QVariant>. And the
> > QVariant contains a QDBusArgument instead of MyUserType.
> >Is this intended behaviour?
> Yes, it's the intended behaviour. It's the "lazy demarshaller" I invented
> (dubbed Pattern Buffer). What it does is that it decodes only what it
> unambiguously knows about: integers, floating point, strings (includes
> object path and signature), as well as array of string and array of
> bytes.
> Anything else gets shoved into a "QDBusArgument" for later decoding.
> The technical reason for that is that a signature of, for instance, "(ii)"
> could be produced by more than one user type (e.g., QPoint and QSize).
> The marshaller can't know what to do in those cases.
> >Isn't is possible to demarshall it already and provide a MyUserType in
> >the QVariant?
> No, for the reasons above.
> >And if not, is there a generic way for me to demarshall it manually into
> > the registered user types so I can provide a clean QVariant-based
> > interface in my Message class?
> qdbus_cast<> does that for you. For example:
> QVariantList::Iterator it = reply.begin();
> for ( ; it != reply.end(); ++it)
>     if (it->userType() == qMetaTypeId<QDBusArgument>())
>         *it = qdbus_cast<MyUserType>(*it);
> This will translate all QDBusArguments to MyUserType. If the conversion
> fails, the QVariant will be null, so you can try multiple conversions to
> see which one works.
> You can also do:
>     QDBusArgument arg = qvariant_cast<QDBusArgument>(*it);
> and then analyse currentSignature() if you have more than one type.

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