[Development] About ALIAS in Q_PROPERTY

[Konstantin Ritt]

Since moc is unable to do safety checks for such complex expressions (in
this case, `if (ui && ui->customWidget)`), this makes Q_PROPERTY
potentially unsafe and the idea has no any value to me.
Simply do s/ui->customWidget/parent()->customWidget/g and imagine what
could happen there...

P.S. @Olivier: "Svetkin" is a family name.

Regards,
Konstantin


2014-03-12 13:48 GMT+02:00 Olivier Goffart <olivier at woboq.com>:

> On Monday 10 March 2014 17:43:35 Giuseppe D'Angelo wrote:
> > Can you please explain what this feature is about, why do you think
> > it's useful, how it's supposed to be used, etc.?
> >
> > On 10 March 2014 17:30, mikhail.svetkin at gmail.com
> >
> > <mikhail.svetkin at gmail.com> wrote:
> > > Hello, I would like to clarify wherein the complexity
> > > (https://codereview.qt-project.org/#change,80412)?
> > > Ready to listen to any suggestions and implement them.
>
> This is a follow-up on the earlier discussion:
> "About Q_PROPERTY in custom widget plugin for designer"
>
> Svetkin's first idea was to extend the READ and WRITE attributes to be more
> complex expressions such as:
>
>   Q_PROPERTY(QString label READ ui->customWidget->label
>                            WRITE ui->customWidget->setLabel)
>
> And he even made a patch for it: (https://codereview.qt-project.org/77758)
> There was small issues with the patch. Notably on how complex can the
> expression be, and also on the fact that it would still be hard to have a
> NOTIFY signal.
>
> I was also wondering if it would not be better to copy QML's idea of
> property
> aliases:
>
>  Q_PROPERTY(QString label ALIAS CustomWidget ui->customWidget->label)
>
> However, now that Svetkin proposed a patch, I feel that it is not so much
> of a
> good idea. I think the syntax is not so nice especially the need to have
> both
> the class name and the 'path' to the property. And also because the notify
> signal is still not automatic.
>
> And overall, i find myself preferring the first idea better. Hence I would
> like more opinions from the list.
>
> The other question is if we should have that at all. How common is it to
> have
> property alias like this?
>
> --
> Olivier
>
> Woboq - Qt services and support - http://woboq.com - http://code.woboq.org
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