SQLite3 Master/Detail | Can't get data in the Detail table

[mrjj]

@landslyde
Hi
Why are you using q.isValid() and not
http://doc.qt.io/qt-5/qsqlquery.html#next

Normally to loop the result is like

   QSqlQuery query("SELECT country FROM artist");
    while (query.next()) {
        QString country = query.value(0).toString();
        ...      
    }

Did i miss something ?

[JonB]

@landslyde
I copied your use of q.isValid() from your code, I didn't look it up. @mrjj's code is the correct way. Also that might explain your problems...!

[A Former User]

@mrjj - That was the key to the door. I'm learning. I'm not here to roach code, just to learn. I just didn't know enough to sort that out and get it headed in the right direction. And thank you for the link. Pure gold!

[A Former User]

@JonB - Your input was appreciated nonetheless. My initial code up there was a hack from a video I watched. While it worked, it wasn't even close to what I know Qt can offer. I hope you guys don't mind my questions. I'm full of them. Really enjoying Qt. Hands down, it's the best!

[mrjj]

@landslyde
We basically hang around here for questions. ;)
So if you show code,
clearly state what you tried,
what you got and what you expected you will find us
very willing to try to help.

Also the online Docs are excellent.

[A Former User]

@mrjj - Thank you very much for the welcome. I do have one more question regarding all we've talked abt here. Although my initial post on this was sloppy code, it did fill the TableWidget properly. Now it won't load the four names I have in it.

void MainWindow::FillTable()
{
    loading = true;
    QSqlQuery q(db);

    int r = 0, c = 0;

    if (!q.exec("SELECT recipe_id, name FROM recipes "
                "ORDER BY name")) db.lastError().text();
    while (q.next())
    {
        ++r;
        ui->tw_recipes->insertRow(r);
        for (c = 0; c < 2; ++c)
        {
            qDebug() << r;
            qDebug() << c;
            qDebug() << q.value(c);
            ui->tw_recipes->setItem(r, c, new QTableWidgetItem(q.value(c).toString()));
        }
    }
    loading = false;
}

Output is:

10:55:47: Starting /home/slyde/Desktop/Qt Apps/build-Crumbs-Desktop_Qt_5_11_0_GCC_64bit-Debug/Crumbs...
1
0
QVariant(qlonglong, 3)
1
1
QVariant(QString, "Cat Finger Licks")
2
0
QVariant(qlonglong, 4)
2
1
QVariant(QString, "Chocolate Chip Cookies")
3
0
QVariant(qlonglong, 2)
3
1
QVariant(QString, "Lemon Cookies")
4
0
QVariant(qlonglong, 1)
4
1
QVariant(QString, "Oatmeal Pecan Chewy")

This line of code worked before, but now it doesn't:

ui->tw_recipes->setItem(r, c, new QTableWidgetItem(q.value(c).toString()));

Why wld it not work? Is there something wrong with it? Please advise.

Pics of this: https://imgur.com/MsJ9xac and https://imgur.com/iQ4mGoI

UPDATE
I added a line to it and see that when I insert a row, nothing happens. Look:

void MainWindow::FillTable()
{
    loading = true;
    QSqlQuery q(db);

    int r = 0, c = 0;

    if (!q.exec("SELECT recipe_id, name FROM recipes "
                "ORDER BY name")) db.lastError().text();
    while (q.next())
    {
        ++r;
        ui->tw_recipes->insertRow(r);  // NOTHING HAPPENS HERE
        for (c = 0; c < 2; ++c)
        {
            qDebug() << r;
            qDebug() << c;
            qDebug() << ui->tw_recipes->currentRow();  // I ADDED THIS LINE TO IT
            qDebug() << q.value(c);
            ui->tw_recipes->setItem(r, c, new QTableWidgetItem(q.value(c).toString()));
        }
    }
    loading = false;
}

And the output:

11:18:16: Starting /home/slyde/Desktop/Qt Apps/build-Crumbs-Desktop_Qt_5_11_0_GCC_64bit-Debug/Crumbs...
1
0
-1
QVariant(qlonglong, 3)
1
1
-1
QVariant(QString, "Cat Finger Licks")
2
0
-1
QVariant(qlonglong, 4)
2
1
-1
QVariant(QString, "Chocolate Chip Cookies")
3
0
-1
QVariant(qlonglong, 2)
3
1
-1
QVariant(QString, "Lemon Cookies")
4
0
-1
QVariant(qlonglong, 1)
4
1
-1
QVariant(QString, "Oatmeal Pecan Chewy")

What's making it be -1?

[mrjj]

Hi
I assume TW is tableWidget ?
Please read this. it shows how its expected to be used.
https://wiki.qt.io/How_to_Use_QTableWidget

You might need to tell it how many to expect/have
m_pTableWidget->setRowCount(10);
m_pTableWidget->setColumnCount(3);

normally to add one new row, you can do
tableWidget->insertRow( tableWidget->rowCount() );

The -1 is most likely
qDebug() << ui->tw_recipes->currentRow();
which means None selected. (since nothing been clicked on)

also
++r; // is 1
ui->tw_recipes->insertRow(r); // ask it to add row at 1 but it dont have row zero so it cant.

[A Former User]

@mrjj - Finally got it! Thanks for all your help.

void MainWindow::FillTable()
{
    loading = true;
    QSqlQuery q(db);

    int r = 0, c = 0;
    if (!q.exec("SELECT COUNT(*) FROM recipes")) db.lastError().text();
    q.first();
    int rCount = q.value(0).toInt();

    if (!q.exec("SELECT recipe_id, name FROM recipes "
                "ORDER BY name")) db.lastError().text();
    while (q.next())
    {
        ui->tw_recipes->setRowCount(rCount);
        for (c = 0; c < 2; ++c)
        {
            ui->tw_recipes->setItem(r, c, new QTableWidgetItem(q.value(c).toString()));
        }
        ++r;
    }
    loading = false;
}

[mrjj]

Hi
super.
One note.
should it not be
int rCount = q.value(0).toInt();
ui->tw_recipes->setRowCount(rCount);

instead of inside the while loop ?

[JonB]

@landslyde
Now be brave and remove the whole SELECT COUNT(*) and the setRowCount(), do it with insertRow() instead. Do it now! You know it makes sense ;-)

Separately, your db.lastError().text(); just returns the text, you won't see anything when your exec()s fail. You will want more like:

qDebug << db.lastError().text();
return ...;

[A Former User]

@JonB - I cldnt make inserRow() work. I'll mess around with it, but not just yet. Yes, it makes more sense doing it that way. I had the variable r stuck in it: insertRow(r), which seems right to me. But it was DOA each time I ran it. I'll work with it though. And I appreciate all of your help, including the addition that came in while I was responding here, regarding using qDebug for lastError(). Thanks.

UPDATE
Works like a charm! =)

void MainWindow::FillTable()
{
    loading = true;
    QSqlQuery q(db);

    int r = 0, c = 0;

    if (!q.exec("SELECT recipe_id, name FROM recipes "
                "ORDER BY name")) 
        qDebug() << db.lastError().text();
    while (q.next())
    {
        ui->tw_recipes->insertRow(r);
        for (c = 0; c < 2; ++c)
        {
            ui->tw_recipes->setItem(r, c, new QTableWidgetItem(q.value(c).toString()));
        }
        ++r;
    }
    loading = false;
}

[A Former User]

@mrjj - Both ways work. But one looks cleaner than the other: yours =) Anyway, the ribs are ready to be pulled out of the smoker, and that means I'm out of here! =)

Thank you for all your help. I'll get there...in time.