QSqlDatabase driver problem

[croscato]

Hi all!

I have the following code:

#ifndef QMYSQLCONNECTION_H
#define QMYSQLCONNECTION_H
 
#include <QObject>
#include <QSqlDatabase>
 
class QMysqlConnection: public QObject, protected QSqlDatabase
{
    Q_OBJECT
 
    friend class QMysqlTable;
 
public:
    QMysqlConnection(const QString& host, const QString& user, const QString&
            password, const QString database, QObject* = 0);
 
    bool isOpen(void) const;
    void close(void);
};
 
#endif // QMYSQLCONNECTION_H

#ifndef QMYSQLCONNECTION_H
#define QMYSQLCONNECTION_H

#include <QObject>
#include <QSqlDatabase>

class QMysqlConnection: public QObject, protected QSqlDatabase
{
    Q_OBJECT

    friend class QMysqlTable;

public:
    QMysqlConnection(const QString& host, const QString& user, const QString&
            password, const QString database, QObject* = 0);

    bool isOpen(void) const;
    void close(void);
};

#endif // QMYSQLCONNECTION_H

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#include <QDebug>
#include <QSqlError>
 
#include "QMysqlConnection.h"
 
// Public functions
QMysqlConnection::QMysqlConnection(const QString& host, const QString& user,
        const QString& password, const QString database, QObject* parent):
        QObject(parent)
{
    this->addDatabase("QMYSQL");
 
    this->setHostName(host);
    this->setUserName(user);
    this->setPassword(password);
    this->setDatabaseName(database);
 
    this->open();
 
    qDebug() << "Last connection error = " << this->lastError();
}
 
bool QMysqlConnection::isOpen(void) const
{
    return QSqlDatabase::isOpen();
}
 
void QMysqlConnection::close(void)
{
    QSqlDatabase::close();
}

#include <QDebug>
#include <QSqlError>

#include "QMysqlConnection.h"

// Public functions
QMysqlConnection::QMysqlConnection(const QString& host, const QString& user,
        const QString& password, const QString database, QObject* parent):
        QObject(parent)
{
    this->addDatabase("QMYSQL");

    this->setHostName(host);
    this->setUserName(user);
    this->setPassword(password);
    this->setDatabaseName(database);

    this->open();

    qDebug() << "Last connection error = " << this->lastError();
}

bool QMysqlConnection::isOpen(void) const
{
    return QSqlDatabase::isOpen();
}

void QMysqlConnection::close(void)
{
    QSqlDatabase::close();
}

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This returns me the following error:
QSqlError(-1, "Driver not loaded", "Driver not loaded")

But if I change this code

this->addDatabase("QMYSQL");
 
this->setHostName(host);
this->setUserName(user);
this->setPassword(password);
this->setDatabaseName(database);
 
this->open();

this->addDatabase("QMYSQL");

this->setHostName(host);
this->setUserName(user);
this->setPassword(password);
this->setDatabaseName(database);

this->open();

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to this code:

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
 
db.setHostName(host);
db.setUserName(user);
db.setPassword(password);
db.setDatabaseName(database);
 
db.open();

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");

db.setHostName(host);
db.setUserName(user);
db.setPassword(password);
db.setDatabaseName(database);

db.open();

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it works! Why this code works and the other code not?

[caduel]

addDatabase returns a QSqlDatabase object.
You'd have to assign it to *this.
(Your own object still has/is/uses a default-constructed (i.e. not initialized) QSqlDatabase.)

HTH

[croscato]

A used the following code and the problem was solved:

QMysqlConnection::QMysqlConnection(const QString& host, const QString& user, const QString& password, const QString database, QObject* parent):
QObject(parent), QSqlDatabase(QSqlDatabase::addDatabase("QMYSQL"))

QMysqlConnection::QMysqlConnection(const QString& host, const QString& user, const QString& password, const QString database, QObject* parent):
QObject(parent), QSqlDatabase(QSqlDatabase::addDatabase("QMYSQL"))

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Thanks...