converting QVariant to QList

[mzimmers]

Hi all -

I'd like to convert a QVariant to a QList, like this (if possible):

class EquipmentItem
{
    Q_GADGET
    ...
}
typedef QList<EquipmentItem> ZoneEquipmentList;
QVariant qv; //  does contain something in my real app.
ZoneEquipmentList zel = qv.toList();

In reading about this, I found this:

QList<QVariant> QVariant::toList() const
Returns the variant as a QVariantList if the variant has userType() QMetaType::QVariantList. If it doesn't, QVariant will attempt to convert the type to a list and then return it. This will succeed for any type that has registered a converter to QVariantList or which was declared as a sequential container using Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE. If none of those conditions are true, this function will return an empty list.QList<QVariant> QVariant::toList() const

I can't find anything on registering a converter. Can someone point me to the correct page for this?

Thanks...

PS: how best to format a passage from one of the Qt docs?

[Chris Kawa]

Simply use

ZoneEquipmentList zel = qv.value<ZoneEquipmentList>();

toList would give you QVariantList, not ZoneEquipmentList, meaning each element would be QVariant that you'd have to convert to your type. It's unnecessary overhead to convert them back and forth.

[mzimmers]

@Chris-Kawa that approach gives me a list of size 0. Do I need to write a converter for my list class?

[JonB]

@mzimmers said in converting QVariant to QList:

QVariant qv; // does contain something in my real app.

Can we start by making 100.0% sure we know what is in there? If qv.value<ZoneEquipmentList>() is empty list what does qv.toList() give you? And if that does give you something, what is inside the QVariant's in the list?

[mzimmers]

@JonB I just spoke with the author of the back end -- we had a misunderstanding about the contents of the message.

To answer your question, toList() does return a size of 1. But it's merely a UUID, not an actual equipment object as I'd expected.

I think my question is answered, but I'll hold off on closing this topic until I do a bit more experimentation.

Thanks...