QVariant to QList

mzimmers

Hi all -

I'm fooling around with a Model, and am trying to figure out how to correctly code the setter. Here's the relevant code:

struct ActivityItem {
    QString name;
    QList<QString> equipment;
    bool recommended;
};

bool ActivityModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    switch (role) {
        item.equipment.clear();
        item.equipment.append(value.toList()); // error: No matching member function for call to 'append'

The last line isn't right, but the error message isn't very helpful, and the code seems to match the doc (as far as I can tell). Can someone give me an idea of what I'm doing wrong here?

Thanks...

JoeCFD

It seems that value.toList() returns QList<QVariant>, not QList<QString>. You may need explicit conversion.

mzimmers

This doesn't work either:

QList<QString> qls = static_cast<QList<QString>>(value.toList());

I think I'm overlooking something fairly basic here.

JoeCFD

@mzimmers said in QVariant to QList:

QList<QString> qls = static_cast<QList<QString>>(value.toList());

I am not sure static_cast works. Can you try to convert one after another with toString() in the list?

JonB

@mzimmers
I don't think a list of variants is/can be the same thing as a list of strings, or converted between the two/treated as such? (A QVariant cannot be a QString, it can only contain one.) My thought is you would want to iterate, appending each element?
Note that this is purely a guess as I read this :)

mzimmers

@JonB I think you're saying basically the same thing that @JoeCFD is, and I think you're both right.

But I still don't know how to cast/convert my QVariant value into a QString (or a QList<QString>).

EDIT: though this comes close:

            for (QString qs : value.toStringList()) {
                item.equipment.append(qs);
            }

EDIT 2: which means this comes even closer:

        case EquipmentRole:
            item.equipment.clear();
            item.equipment.append(value.toStringList());

JoeCFD

@mzimmers item.equipment.append(value.toStringList()); is a good one. Does it work?

mzimmers

@JoeCFD I can't tell for sure until I can expose this in QML, but I'm fairly sure it's working. I'll ask my other question in the QML forum.

Thanks for the help, guys.

EDIT: yeah, it seems to have worked.

JoeCFD

@mzimmers

got this from ChatGPT and you are good.
if (variant.canConvert<QStringList>()) {
QList<QString> stringList = variant.toStringList();
}

mzimmers

@JoeCFD yeah, I saw the canConvert() method in the docs, but forgot to add it to my code. Thanks for the reminder.

JonB

@JoeCFD said in QVariant to QList:

got this from ChatGPT

Depressing! :(

JoeCFD

Understand. Think about you can never be the number 1 or even close anymore if you play chess.

mzimmers

@JoeCFD said in QVariant to QList:

Understand. Thiink about you can never be number 1 anymore if you play chess.

Oddly enough, that was never a concern of mine.