[Interest] QMetaProperty::write behavior changed with Qt 5.6 - Bug?

[Christian Ehringfeld]

I see the problem.
Thank you for pointing that out!

Since then I have
been thinking about how to solve this, but having been been fine with
staying on Qt 5.5 for the time being I've had no pressure to - but
with Qt5.7 there are some gui-features which I want use, so I really
have to solve my dilemma.





I have to set List
properties of different objects, all derived from "Entity".





Because of
abstracted methods,  in my context I can only see 

QList<QSharedPointer<Entity>>

and not 

QList<QSharedPointer<Person>>

(Where Person
derives from Entity)





<code>

void
Class::setListProperty(const QSharedPointer<Entity> &entity,
QList<QSharedPointer<Entity>> &list, const
QMetaProperty &property)  {    

    QVariant var;   
var.setValue<QList<QSharedPointer<Entity>>>(list); 
 

    
QVERIFY(property.write(entity.data(), var));

}

</code>





With an
EntityInstanceFactory it's possible to instantiate an object of the
actual class (e.g. Person) and I can see its classname ("Person")
as a string, too - 





But the interface
type is, of course, still: QList<QSharedPointer<Entity>>
- and that is not enough, because for the use of QMetaProperty::write
I do understand that I need <QList<QSharedPointer<Person>>.





I'd happily use
templates, but at compile time there is no way to know what the
specific class will be, as data is being retrieved at runtime from a
data base.





Any idea how I can
get an instance of QList<QSharedPointer<Person>> in this
context?

Am Freitag, den 06.05.2016, 22:26 -0700 schrieb Thiago Macieira:
> On sábado, 7 de maio de 2016 01:36:42 PDT Christian Ehringfeld wrote:
> > Yes, you can find it here:
> > https://github.com/Professi/metaproperty-write-test
> > Test fails under Qt 5.6 and is succesful under Qt 5.5.1.
> > > > When I remove the inheritance between person and entity it also
works
> > with Qt 5.6.
> 
> > You're trying to set a property of type QList<QSharedPointer<Person>>
with a 
> > variant containing QList<QSharedPointer<Entity>>. That's not supposed
to work 
> because lists in C++ do not support covariance nor contravariance.
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/interest/attachments/20160827/39436094/attachment.html>