How can I get previous data of QTableWidgetItem?

Aaron Kim

itemChanged(QTableWidgetItem * item) signal can not retrieve previous(before change) data.
I can't find other signals which suit this case.

JonB

@Aaron-Kim
Since there does not appear to be some beforeItemChanged() signal, unless you know just what will cause the item changed in your code (e.g. can you look at the model's setData() perhaps?) you are on your own. You would have to have stored up the data's previous value yourself somewhere. I don't think you're supposed to try to get back at old data from the view, I think you're supposed to do it from the model side.

Taz742

@Aaron-Kim
You need to save it somewhere.

Something like this:
.h file

private:
    vector<vector<QString> > arr;

.cpp constructor:

    for (int i = 0; i < 10; i++) {
        vector<QString> t;
        for (int j = 0; j < 5; j++) {
            t.push_back(QString("%1, %2").arg(QString::number(i), QString::number(j)));
        }
        arr.push_back(t);
    }

    ui->tableWidget->setColumnCount(5);
    ui->tableWidget->setRowCount(arr.size());

    for (int i = 0; i < 10; i++) {
        for (int j = 0; j < 5; j++) {
            ui->tableWidget->setItem(i, j, new QTableWidgetItem(arr[i][j]));
        }
    }

    connect(ui->tableWidget, &QTableWidget::itemChanged, this, [=](QTableWidgetItem *item) {
        int row = item->row();
        int column = item->column();
        qDebug() << "previous value: " << this->arr[row][column];
        qDebug() << "new value: " << item->text();
        this->arr[row][column] = item->text();
    });

Aaron Kim

Thanks. It seems that it is the only way.

VRonin

Requires Qt >= 5.11

QObject::connect(tableWidget->model(),&QAbstractItemModel::dataChanged,[=](const QModelIndex& topLeft, const QModelIndex& bottomRight, const QVector<int>& roles){
    if(!roles.isEmpty() && !roles.contains(Qt::EditRole))
        return;
    for(int i=topLeft.row();i<=bottomRight.row();++i){
        for(int j=topLeft.column();j<=bottomRight.column();++j){
            const QModelIndex currIdx = topLeft.model()->index(i,j,topLeft.parent());
            qDebug() << i << ";" << j << " Previous Value: " << currIdx.data(Qt::UserRole);
            tableWidget->model()->setData(currIdx, currIdx.data(Qt::EditRole), Qt::UserRole);
        }
    }
});