Qt 5 -> Qt 6 Stream operator for QVariant

[kazaak]

I created a class that overloads the stream operator to read binary data. The implementation streams several variables to unpack a binary file like below:

QDataStream &operator >>(QDataStream &stream,KItem &item) {

    stream >> item.itemTargetType;
    stream >> item.itemTarget;
    stream >> item.itemLabelName;
    stream >> item.itemLabelFont;
    stream >> item.itemLabelforegroundColor;
    stream >> item.itemLabelbackgroundColor;
    stream >> item.lockAspectRatio;
    stream >> item.itemImagePixmap;
    stream >> item.itemImageSize;
    stream >> item.datatagFilename;

    stream >> item.datatagTreeValues;

    return stream;
}

Everything worked fine in 5.15.2 but in 6.4.3 all the variables but the last one load. It's very nested along the lines of QHash<QString, QVariant> And the QVariant contains QVariantLists of QVariants, QPixmaps, QStringLists, and QDateTime. All these types are in QMetaType but they aren't loading and I get an empty QHash with this in the output:

Trying to construct an instance of an invalid type, type id: 65
Trying to construct an instance of an invalid type, type id: 16640
Trying to construct an instance of an invalid type, type id: 16640
Trying to construct an instance of an invalid type, type id: 18432
Trying to construct an instance of an invalid type, type id: 3539043

Does the nested QMetaTypes need to be registered as it's own type? If so, I don't know how to go about that since the QVariantList can contain a variable number and structure of QMetaTypes.

[ChrisW67]

@kazaak If the data you are reading was written by Qt 5.x then you may need to call QDataStream::setVersion() to allow the Qt6 implementations to adapt

[kazaak]

@ChrisW67 Excellent! That was the issue and all bugs resolved. Quite the ctrl+F exercise for my entire project but I don't see another way around. Looks like support for previous stream versions will be there for a while. Thanks for the fast reply!