Subclassing QColor

rheniser

I would like to extend the QColor class by adding a few class member functions. Can I just subclass QColor? I read the Creating Custom Qt Types. But, that appears to be more for object composition. I want to inherit all the lovely functions already in QColor.

Thanks,
Ryan

Anticross

You can do multiple sub classing from QColor and QObject.

andre

[quote author="rheniser" date="1329264613"]I would like to extend the QColor class by adding a few class member functions. Can I just subclass QColor? I read the Creating Custom Qt Types. But, that appears to be more for object composition. I want to inherit all the lovely functions already in QColor.

Thanks,
Ryan[/quote]
Yes, you can subclass QColor. However, be aware that this class was not designed to be subclassed, as it does not have a virtual destructor. If you start adding members, those might not be properly destructed if you use your subclass as a normal QColor.

I don't understand the suggestion for multiple inheritance above. It does not seem to apply, and is generally a practice to avoid for anything but interfaces, IMHO.

rheniser

Yes, the missing virtual destructor in the header is what prompted me to ask. Thanks for the insight. Out of curiosity, will my derived class work with Qt containers and QVariant::value() or the qvariant_cast() template function?

andre

Qt containers will work as long as your class is copyable and default constructable. If you register your class, then QVariant, Q_PROPERTY and queued signals-slot connections will also work. See the [[doc:QMetaType]] documentation for details on that. If you also need streaming to work for those QVariants, don't forget to implement operator>>() and operator<<() for the type.

rheniser

Alas, cspec is private and has no mutator function. I think an adapter class is the best way forward here.