QVariant var; if(var.isNull()) { qDebug() << "The QVariant object is null"; }
QVariant var; var = QVariant::Null; if(var.isNull()) { qDebug() << "The QVariant object is now null"; }
QVariant var = QVariant(QVariant::String); if(var.isNull()) { qDebug() << "The QVariant object with null string value is created"; }It is a part of the QtCore package.