QTableWidget See difference between 0 and NULL

hobbyProgrammer

I have an application that insert data into a database from a qtablewidget. The tablewidget has 100 rows, but not all need to be filled in to insert into the database.
The data shouldn't be NULL but can be 0.

I tried to filter it like this:

int dataID = getDataID(ui->listView->currentIndex().data().toString());

    for(int i = 0; i < ui->tableWidget->rowCount(); i++)
    {
        int col0 = NULL;
        int col1 = NULL;
        int col2 = NULL;

        for(int j = 0; j < ui->tableWidget->columnCount(); j++)
        {
            if(ui->tableWidget->item(i, j)->text() != nullptr)
            {
                if(j == 0)
                {
                    col0 = ui->tableWidget->item(i, j)->text().toInt();
                }
                else if(j == 1)
                {
                    col1 = ui->tableWidget->item(i, j)->text().toInt();
                }
                else if(j ==2)
                {
                    col2 = ui->tableWidget->item(i, j)->text().toInt();
                }
            }
        }
        if(col0 != NULL &&
           col1 != NULL &&
           col2 != NULL)
        {
            insertData(dataID, col0, col1, col2);
        }
    }

But this won't see the difference between 0 and NULL

Is there anyone who can help me with this?
I only need to know how to see the difference between 0 and NULL.

sierdzio

@hobbyProgrammer said in QTableWidget See difference between 0 and NULL:

I only need to know how to see the difference between 0 and NULL.

0 and NULL are the same thing (typedef). There is no difference and there won't be any.

If you want to have some value to act as "not set", use -1. Or some custom type / struct that will have a distinction between a set number and not set number.

hobbyProgrammer

@sierdzio Is it possible to change this by making a custom tableview?
this = seeing the difference between null and 0.

I really don't want to set each cell to -1 as a start value, since this will be seen in the tableview and I don't want that.

sierdzio

You can't change the NULL typedef. It's got nothing to do with table view, it is defined in core C++ headers (stddef.h). You can, however, create some custom struct and use that in your table, instead of int.

HoMa

I guess the "dataWidgetItem" has a "data" method that returns a Variant. Did you try "isValid" or "isNull" on that before inserting the data?
Regards
Holger

sierdzio

Hey, but I suppose your table is really holding QVariant, right? Then sure, you can check QVariant::toString().isEmpty() - if true, then you don't have any value set. Possibly even QVariant::isNull() will work.

JonB

@hobbyProgrammer
After fetching data from database, https://doc.qt.io/qt-5/qvariant.html#isNull or (if you are SQL) https://doc.qt.io/qt-5/qsqlfield.html#isNull is the thing to test.