How to access QSqlRelationalModel from function?

mrjj

@Panoss
Yes but it jsut says. Programs crashed.
So find your error using the debugger :)

If i should guess

i think
RepairDevices::RepairDevices()
{
repairsmodel = new QSqlRelationalTableModel(this);
}

is never called and you crash at this line
repairsmodel->setFilter("id>76"); // use it
since repairsmodel is just a dangling pointer.

Panoss

mrjj forgive my ignorance, I'm a total newbee.
I suppose this is the error:
...repairdevices.cpp:115: error: Exception at 0x4029fb, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance)

mrjj

@Panoss
Ok fair enough.

The errors says that something in the program was fiddling around with some memeory it should not.

so try this and tell me if crash goes away


RepairDevices::RepairDevices()
{
 //////   OUT	repairsmodel = new QSqlRelationalTableModel(this);
}
	
void refresh_devices_search_tbl(){
 // make it here jsut to test
	repairsmodel = new QSqlRelationalTableModel(this); 

	QString sn = ui->sn_search_txt->toPlainText();
	
	repairsmodel->setFilter("id>76");

    qDebug() << "in refresh_devices_search_tbl";
}

also please use
qDebug()
like in sample. it helps alot to see what is called.

Panoss

@mrjj said in How to access QSqlRelationalModel from function?:

@Panoss
RepairDevices::RepairDevices()
{
repairsmodel = new QSqlRelationalTableModel(this);
}

is never called and you crash at this line

I think you 're right, somehow refresh_devices_search_tbl() is called before repairsmodel = new QSqlRelationalTableModel(this);!!!
I don't understand how is this possible...

mrjj

@Panoss said in How to access QSqlRelationalModel from function?:

RepairDevices::RepairDevices()
{
repairsmodel = new QSqlRelationalTableModel(this);
}

This looks like the constructor but most likely you are using the one you get from
QMainWindow that takes a parent.
and hence yours is never called.

show how you create the RepairDevices instance ?

( i mean where you do like )
RepairDevices *mine= new RepairDevices ( ? )

Panoss

In main.cpp, this has this code:

#include "repairdevices.h"
#include <QtWidgets>



int main(int argc, char * argv[])
{
    Q_INIT_RESOURCE(books);

    QApplication app(argc, argv);    

    RepairDevices win;
    win.show();

    return app.exec();
}

mrjj

@Panoss said in How to access QSqlRelationalModel from function?:

Hmm i would have expected it to call
your constructor but it seems not. Mainwindow must have one that qualify.

Well it seems to use the one u get from your
base class and hence yours is never called.

so that is why.

Using a debugger this would be really clear :)

a normal mainwindow constructor looks like this

explicit MainWindow(QWidget *parent = 0);

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
}

Panoss

@mrjj said in How to access QSqlRelationalModel from function?:

@Panoss said in How to access QSqlRelationalModel from function?:

Hmm i would have expected it to call
your constructor but it seems not.
I thought 'RepairDevices win' calls the constructor.

@mrjj said in How to access QSqlRelationalModel from function?:

@Panoss said in How to access QSqlRelationalModel from function?:
Using a debugger this would be really clear :)
I did use the debugger but it was not clear at all to me :).

It still isn't, what must I do?
I ''l do mainwindow constructor as you suggested and post the result.

I did the test you suggested me above, I had to change a dot to -> (ui->sn_search_txt to ui.sn_search_txt)

        repairsmodel = new QSqlRelationalTableModel(this);
        QString sn = ui.sn_search_txt->toPlainText();
        repairsmodel ->setFilter("id>76");
        qDebug() << "in refresh_devices_search_tbl";

and got no error.
The etext is not printed, so the refresh_devices_search_tbl is not called now.

mrjj

@Panoss said in How to access QSqlRelationalModel from function?:

refresh_devices_search_tbl

who calls it ?
Is it a slot for a button or how should it be called?

Panoss

It 'a a slot for two combo boxes and two textboxes.
It 's called on textChanged and currentIndexChanged.
(omg text and index of combos I think do get changed during form's load, e.g when they are mapped to the data mapper.)

mrjj

@Panoss
well just check the
connects and its should be clear why its not called.
(connect return true / false)

At some point you will also need to learn to use the debugger and set break points.
Its THE BEST tool to find out what is happening and where program goes. :)

Panoss

I found the guilty!!With the debugger.
It's a combo box which calls the function at oncurrentIndexChanged event!
This means that when a combo gets data from a model, the oncurrentIndexChanged event is called!!
How can I fix this?

mrjj

@Panoss
I think its by design.
When it get data, the current
index is changed so its correct to
emit the signal.
Check current index before and after and see.

Most likely its 100% correct and you might need to use other signal or
wait until after the data load to set the connect.

ps. Good work with debugger :)

Panoss

Can I do something like this?

ui.type_search_cbo->cancelEventoncurrentIndexChanged;
ui.type_search_cbo->setModel(model);
ui.type_search_cbo->resetEventoncurrentIndexChanged;

(nice code, eh?)

mrjj

@Panoss

well i would prefer if you could just wait to connect the slots
so its ok it says index changed.

There is
http://doc.qt.io/qt-5/qobject.html#blockSignals

but again, you are fixing a symptom so it not the best.

Panoss

Yes, it works with block signals.
So, this is not the correct remedy?

How could I wait to connect the slots?
I don't want just to fix the symptom, I want to do it properly.

mrjj

@Panoss
well where do you hook up the oncurrentIndexChanged signal?

Panoss

It's a slot for a combo:

void RepairDevices::on_type_search_cbo_currentIndexChanged(int index)
{
    refresh_devices_search_tbl(); 
}

mrjj

@Panoss said in How to access QSqlRelationalModel from function?:

Ah you are using the auto connect feature?
you do not have connect( xxxx) , correct ?

Panoss

No, I don't even know what autoconnect is.
I have no connect( xxxx) for this function.
(unless you 're meaning that this way, it 's autoconnected)