Seas Robert,
If memory serves well, there was a recent post about the same question on the
Qt Forum.
Haven't got around to answer, because I wanted to read some code upfront.
The given implementation of getBindable() has no return type, but you say it's
a bindable.
I also assume that there's a reason for actually returning a bindable, rather
than a qreal value.
Probably a calculation is implemented.
The code looks safe to me. The only caveat could be, that the propery is
actually qreal typed.Depending on how it changes hands in QML, it might become
a qreal value at some point, hence loosing the actual binding. But that's not
related to your implementation.
I still find it unusual and haven't seen it anywhere else, than in the
mentioned example.
Don't fully understand the use case of it. But you sound like you do 🙂, so IMHO
there's nothing to worry about.
Cheers,
Axel
________________________________
Von: Interest <interest-boun...@qt-project.org> im Auftrag von Schimkowitsch
Robert <robert.schimkowit...@andritz.com>
Gesendet: Freitag, 24. Mai 2024 14:08
An: interest@qt-project.org <interest@qt-project.org>
Betreff: [Interest] Is it safe to construct QBindable from QProperty* via
QUntypedBindable?
I use QBindable a lot in C++ classes that expose properties to QML.
My typical property implementation looks as follows:
Q_PROPERTY(qreal x BINDABLE getBindableX READ default FINAL)
//...
QProperty<qreal> m_X;
//...
CPropertyClass::getBindableX() const
{
return &m_X;
}
I got the idea to use "&m_X" to get the QBindable for a property from the
example in QObjectBindableProperty. And initially, I also used
QObjectBindableProperty via Q_OBJECT_BINDABLE_PROPERTY macro.
But once QML natively supported BINDABLE properties, I no longer saw any
advantage, and using QProperty produces less boilerplate.
So the usage of "&m_X" to get QBindable is documented for
QObjectBindableProperty, but only in the example, not in the docs specifically.
It feels a bit dirty to create a derived class via promotion from a base class.
And for QProperty, "&m_X" is not documented even in an example.
So the question is: Is it safe to use? Have I misunderstood something by
choosing QProperty over Q_OBJECT_BINDABLE_PROPERTY?
Robert Schimkowitsch
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