How to access QSqlRelationalModel from function?

Panoss

This is my header:

class RepairDevices: public QMainWindow
{
    Q_OBJECT
public:
    RepairDevices();    


private slots:
	void refresh_devices_search_tbl();
	
private:
    void setupDevices();
    void setupRepairs();       
    Ui::RepairDevices ui;
    
    QSqlRelationalTableModel *repairsmodel;

This is my Source file:

RepairDevices::RepairDevices()
{
	repairsmodel = new QSqlRelationalTableModel(this);
}
	
void refresh_devices_search_tbl(){
	Ui::RepairDevices *ui;
	QString sn = ui->sn_search_txt->toPlainText();
	
	repairsmodel->setFilter("id>76");
}

But It's ending with Error application ended unexpectedly.
Obviously, I 'm doing something very won here.
Which is the correct way to do it?
So I 'll be able to make repairsmodel->setFilter work in my function?

mrjj

Hi

void refresh_devices_search_tbl(){
Ui::RepairDevices *ui; <<<< what is this ? looks nasty, Did you even allocate it ? Looks bad and wrong to me :)
}

why is refresh_devices_search_tbl not member of RepairDevices ?

If it was then repairsmodel is available to it.

RepairDevices::refresh_devices_search_tbl

Panoss

The 'Ui::RepairDevices *ui' I put it for someone to norice it and tell me if it's correct.
I made the function a private member, so now I have access to ui and repairsmodel.
But when the execution goes to repairsmodel->setFilter("id>76") (this is in the function), the application breaks down.
"The program has unexpectedly finished."

I tried in debugging, when code execution goes to repairsmodel->setFilter("id>76"), I get this error:
alt text

mrjj

@Panoss

im not sure what you are doing but just make
refresh_devices_search_tbl a function in
RepairDevices

and you dont need anything else.

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

void RepairDevices::refresh_devices_search_tbl(){
Ui::RepairDevices *ui; // DONT DO THIS. its evil :)

repairsmodel->setFilter("id>76"); // use it

}

Panoss

This error appeared after I did exactly what you 're suggesting.

mrjj

@Panoss
if u still have Ui::RepairDevices *ui
then no wonder :)

Ui::RepairDevices *ui;
QString sn = ui->sn_search_txt->toPlainText(); ///// BIG FAT CRASH HERE

Panoss

I don't have it, I 've deleted it.

mrjj

ok,
then debug it. find where you crash.

This also looks a bit odd to me

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

its that the constructor ?
What about the stuff for QMainWindow ?

Panoss

I told you.I posted the image of the error above.
Isn't it visible?

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. :)