QVariant custom classes polymorphism

Question

I have such a classes hierarchy:

class Base {
...
virtual QWidget* getEditor();
...
}

class Derived {
...
QWidget* getEditor() Q_DECL_OVERRIDE;
...
}

Both classes are registered via Q_DECLARE_METATYPE()

I'm getting instance of Base class from QVariant. Is it possible to get a pointer from QVariant to be able to invoke getEditor() from a Derived object?

I'm trying this atm but have no success:

if (index.data(Qt::EditRole).canConvert<Base>())
    return index.data(Qt::EditRole).value<Base>().getEditor(parent);

This snipper invokes Base class method.

score 1 · Accepted Answer · edited May 23 '17 at 11:58

1

You need to make your base class' function virtual to enable polymorphism:

class Base {
...
virtual QWidget* getEditor();
...
}

class Derived {
...
QWidget* getEditor() Q_DECL_OVERRIDE;
...
}

Also, the way you have it now will cause object slicing. You will need to acquire a pointer to Derived, and call the function on that pointer.

edited May 23 '17 at 11:58

Community

1
1

answered Sep 28 '15 at 13:43

SingerOfTheFall

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Edited my post. The question is how should I get pointer from QVariant::value<>() – Eckler Sep 28 '15 at 13:57
@Eckler, to get the pointer from `QVariant` you must first store that pointer in the `QVariant`, so apparently you will have to change your code to store pointers, not objects. – SingerOfTheFall Sep 28 '15 at 14:08
Should I change Q_DECLARE_METATYPE(Base) to Q_DECLARE_METATYPE(Base*) is this case? – Eckler Sep 28 '15 at 14:24
@Eckler, check something like this http://blog.bigpixel.ro/2010/04/storing-pointer-in-qvariant/ – SingerOfTheFall Sep 28 '15 at 15:01

QVariant custom classes polymorphism

1 Answers1