How can I cast a QVariant to custom class?

问题

I'm developing a BlackBerry 10 mobile application using the Momentics IDE (native SDK).

I have a listview which I want to handle its items click with C++ (I need to use C++ not QML).

I can get the index path using the "connect" instruction, but I have problem with parsing a QVariant to a custom class ;

Q_ASSERT(QObject::connect(list1, SIGNAL(triggered(QVariantList)), this, SLOT(openSheet(QVariantList))));

QVariant selectItem = m_categoriesListDataModel->data(indexPath);

I tried to use the static cast like below

Category* custType = static_cast<Category*>(selectItem);

but it returns :

"invalid static_cast from type 'QVariant' to type 'Category*'"

Can anyone help me on this ?

回答1:

You could try using qvariant_cast and qobject_cast.

QObject *object = qvariant_cast<QObject*>(selectItem);
Category *category = qobject_cast<Category*>(object);

Also, never put any persistent statement into Q_ASSERT. It will not be used when the assert is not enabled.

回答2:

EDIT: works for non QObject derived type (see Final Contest's answer for this case)

First of all, you need to register your type to be part of QVariant managed types

//customtype.h
class CustomType {
};

Q_DECLARE_METATYPE(CustomType)

Then you can retrieve your custom type from QVariant in this way :

CustomType ct = myVariant.value<CustomType>();

which is equivalent to:

CustomType ct = qvariant_cast<CustomType>(myVariant);

来源：https://stackoverflow.com/questions/24362946/how-can-i-cast-a-qvariant-to-custom-class