Empty QComboBox with QSqlQueryModel - sql

Question

I am totally new to Qt and just want to play around a little. I want to try to fill a ComboBox with values from a DB
I have got the following code:
QSqlDatabase db = QSqlDatabase::addDatabase("QODBC");
db.setHostName("LOCALHOST");
db.setDatabaseName("rms32");
if(db.open())
{
QSqlQuery query;
query.prepare("select user_name from T_USER");
if(query.exec())
{
this->model = new QSqlQueryModel();
this->model->setQuery(query);
qDebug() << this->model->rowCount();
qDebug() << this->model->columnCount();
ui->_UsernameCB->setModel(this->model);
//ui->_UsernameCB->setModelColumn(0);
qDebug() << "Last error: " << db.lastError().text();
qDebug() << "Connection opened successfully";
}
db.close();
}
The rowCount and colCount gives me 1, corresponding to my DB, but the user_name is not displayed in the Combobox.
Can anyone point me to the error?

Answer 1

I cannot reproduce your problem. I have the very simply class below inheriting from QComboBox. I went for an sqlite database but otherwise most lines are pretty much exactly as in your case and it correctly displays the one entry in the DB.
If you replace the DB in the code with yours, do you get the entry correctly displayed?
combobox.h
#ifndef MYCOMBOBOX_H
#define MYCOMBOBOX_H
#include <QComboBox>
QT_FORWARD_DECLARE_CLASS(QSqlQueryModel);
class ComboBox : public QComboBox
{
public:
ComboBox(QWidget *widget = 0);
QSqlQueryModel *model;
};
#endif
combobox.cpp
#include "combobox.h"
#include <QSqlDatabase>
#include <QSqlQueryModel>
#include <QSqlQuery>
ComboBox::ComboBox(QWidget *parent) :
QComboBox(parent)
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("db.db");
if(db.open())
{
QSqlQuery query;
query.prepare("select * from TEST");
if(query.exec())
{
this->model = new QSqlQueryModel;
this->model->setQuery(query);
this->setModel(this->model);
}
db.close();
}
}
main.cpp
#include <QApplication>
#include <QDialog>
#include <QHBoxLayout>
#include "combobox.h"
int main(int argc, char** argv)
{
QApplication app(argc,argv);
QDialog dialog;
ComboBox box;
QHBoxLayout layout;
layout.addWidget(&box);
dialog.setLayout(&layout);
dialog.show();
return app.exec();
}