[solved]Total amount of column in TableView/Model

[Harb]

@Mr.-Kibu
Hi! There is no special fucntion to calculate sum. Model is just an interface between your data and view. So if you want to calculate a sum of the column you could just implement special method in your QAbstractItemModel subclass. For example:

int CalcColumnSum(int column)
{
       int s=0;      
       for(int i=0;i<rowCount();++i)  
              s+=index.(i,column,QModelIndex()).data(Qt::DisplayRole).toInt();
       return s;
}

But in fact, as I said before model is just an interface, so you don't need to interact with it to obtain data. You can obtain it directly, because you know your data structure. I don't, that why I made general example

[Mr. Kibu]

Thank you to Harb! When I use your code like this, it works:

    QSqlTableModel *testTab = new QSqlTableModel(this, ConnProjectDB::db());

    testTab->setTable("Test");
    testTab->select();
    ui->tableView->setModel(testTab);

    int s=0;
    for(int i=0;i<testTab->rowCount();++i)
           s+=testTab->index(i,3,QModelIndex()).data(Qt::DisplayRole).toInt();

     QString c = QString::number(s);
     ui->label->setText(c);

But if I subclass the code like this:

h:

private slots:

     int CalcColumnSum(int column, QSqlTableModel model);

cpp:

    QSqlTableModel *testTab = new QSqlTableModel(this, ConnProjectDB::db());

    testTab->setTable("Test");
    testTab->select();
    ui->tableView->setModel(testTab);

    QString c = QString::number(CalcColumnSum(3,testTab));
    
    ui->label->setText(c);


int CalcColumnSum(int column, QSqlTableModel model)
{
       int s=0;
       for(int i=0;i<model.rowCount();++i)
              s+=model.index(i,column,QModelIndex()).data(Qt::DisplayRole).toInt();

}

I get this error-message on building:

"/home/franz/Dokumente/IT/QT/Projekte/BiFF/src/mainwindow.cpp:57: Fehler: no matching function for call to 'MainWindow::CalcColumnSum(int, QSqlTableModel*&)'
QString c = QString::number(CalcColumnSum(3,testTab));
^"

Is there a better way to obtain my data. Where can I obtain it directly (from the database, the tableview, )?
In the future I want to subclass the tableview in a QSortfilterproxymodel like this:
https://doc.qt.io/archives/4.6/itemviews-customsortfiltermodel.html

Than I want to get the total amount from the filtered rows!

Thank you!

[SGaist]

Hi,

You slot signature is the problem. You can't copy a QSqlTableModel object, it's a QObject and their copy is not allowed
.

[Mr. Kibu]

Okay, and what is the correct slot signature instead of "int CalcColumnSum(int column, QSqlTableModel model);"?

[Mr. Kibu]

Is it the right way to add a pointer to the signature like this:

CalcColumnSum(int column, QSqlTableModel *model)

But now I get the error

undefined reference to `MainWindow::CalcColumnSum(int, QSqlTableModel)*

at the position

QString c = QString::number(CalcColumnSum(3,testTab));

Thank's for help!!

Franz

[jsulm]

You have to change the definition of CalcColumnSum(int column, QSqlTableModel *model) in .cpp file as well:
CalcColumnSum(int column, QSqlTableModel *model)
{
...
}

Actually, you can use a reference instead of pointer: CalcColumnSum(int column, QSqlTableModel &model)

[Mr. Kibu]

Sorry, I have not said that I have already changed the definition of CalcColumnSum in cpp to "CalcColumnSum(int column, QSqlTableModel *model)".

But the error is still here!

[SGaist]

On a side note, it's not common practice for slots to return values

[Mr. Kibu]

The difinition of CalcColumnSum is now:

int CalcColumnSum(int column, QSqlTableModel *model)
{

    int s=0;
       for(int i=0;i< model->rowCount();++i)
              s+=model->index(i,column,QModelIndex()).data(Qt::DisplayRole).toInt();

}

But the error is still here ....

[Mr. Kibu]

Very stupid mistake:
I have forgotten to use "MainWindow::" in the definition. Here it is:

void MainWindow::CalcColumnSum(int col,QSqlTableModel *model)
{
...
}