Can't edit text in cell in a dynamic QTable model

jss193

Hello, I am in troubles with my model, I have created a model where I can dinamically add new rows, then I want to edit its text, so I created a vector in my class such as I can dinamically add or modify text, but I obtain the following error:

ASSERT failure in QVector<T>::operator[]: "index out of range", file /Users/aaaa/Qt/5.11.1/clang_64/lib/QtCore.framework/Headers/qvector.h, line 436
19:54:10: The program has unexpectedly finished.

bool Table::setData(const QModelIndex & index, const QVariant & value, int role)
{
     m_gridData = new QVector<QVector<QString>>;

    if (role == Qt::EditRole)
    {
        //save value from editor to member m_gridData
        (*m_gridData)[index.row()][index.column()]= value.toString();
        //for presentation purposes only: build and emit a joined string
        QString result;
        for(int row= 0; row < rows; row++)
        {
            for(int col= 0; col < columns; col++)
            {
                result += (*m_gridData)[row][col];

            }
        }
        emit editCompleted(result);
        return true;
    }
    return false;
}

Why is my index out of range??

Thank you!

mrjj

Hi
The vector is empty so accessing it will crash.
[index.row()][index.column()] can never be valid for empty vector.

if you want to use [][], you should use
~~https://doc.qt.io/qt-5/qvector.html#reserve~~
https://doc.qt.io/qt-5/qvector.html#resize
on both vectors.
so they contain empty strings.
Or use append to add the data.

jss193

You mean change
(*m_gridData)[index.row()][index.column()]= value.toString();

By
(*m_gridData)[row][column]= value.toString();???

Christian Ehrlicher

Again: you can't access to an index which is out-of-bounds and will get an asserting (in debug mode) or undefined behavior (in release mode) - see https://doc.qt.io/qt-5/qvector.html#operator-5b-5d

"i must be a valid index position in the vector (i.e., 0 <= i < size())."

VRonin

Memory Leaks Everywhere

Why are you doing m_gridData = new QVector<QVector<QString>>;?

jss193

I tried this

bool ModelTable::setData(const QModelIndex & index, const QVariant & value, int role)
{
    m_gridData = new QVector<QVector<QString>>;


    if (role == Qt::EditRole)
    {
        //save value from editor to member m_gridData
        (*m_gridData)[index.row()][index.column()]= value.toString();

        //for presentation purposes only: build and emit a joined string

        QString result;
        for(int row= 0; row < rows; row++)
        {
            for(int col= 0; col < columns; col++)
            {
                //result += (*m_gridData)[row][col];
                (*m_gridData).append(QVector<QString>()<<result);

            }
        }
        emit editCompleted(result);
        return true;
    }
    return false;
}

and Initialized the vector in constructor such as:

ModelTable::ModelTable(QObject *parent):QAbstractTableModel (parent)
{
 m_gridData = new QVector<QVector<QString>>;
}

and updated size such as:

bool ModelTable::insertRows(int row, int count, const QModelIndex &parent){
    beginInsertRows(parent,row,row+count-1);
    rows = rows+count;
    endInsertRows();
    qDebug() << rows;
     (*m_gridData)[rows][columns];//update value of matrix
    return true;

and still index out of range.

I did this
(*m_gridData)[index.row()][index.column()]= value.toString();
to store the initial values of table into my m_gridData and update them as the programs is working.

Thanks!

VRonin

None of the above makes any sense.

Why are you subclussing a model anyway? What is the problem with just using QStandardItemModel?

jss193

Because I want it modified by adding new methods later associated with dynamic table. What I wish is to add dinamycally rows by pressing a button, then store data into cells and this data into a vector of vectors to be modified on execution time

VRonin

Everything you described can be done by QStandardItemModel.
Something like:

QAbstractItemModel* model = new QStandardItemModel(this);
model->insertColumns(0,columns);
model->insertRows(0,rows);
model->setData(model->index(0,0),QStringLiteral("One String"));
model->setData(model->index(1,0),QStringLiteral("Another String"));
model->insertRow(1);
model->setData(model->index(1,0),QStringLiteral("Inserted String"));

@jss193 said in Can't edit text in cell in a dynamic QTable model:

I want it modified by adding new methods later

You can always just subclass QStandardItemModel you don't need to start from scratch

mrjj

Hi
Besides i very much agree with @VRonin about using QStandardItemModel
Your current issue is that you use 2 vectors now

bool ModelTable::setData(const QModelIndex & index, const QVariant & value, int role)
{
m_gridData = new QVector<QVector<QString>>; // this is a new one, you add to
...

so
the one you make
ModelTable::ModelTable(QObject *parent):QAbstractTableModel (parent)
{
m_gridData = new QVector<QVector<QString>>;

Might not be used at all and just leak memory or be used in
bool ModelTable::insertRows where its empty and still gives index out of bounds for that reason.