QSqlDatabasePrivate::addDatabase: duplicate connection name 'MyConnection' error

Question

I have written a Qt program in c++ inorder to access a database and load database tables to table view! My program does not show any compile errors but gives 2 runtime errors

QSqlDatabasePrivate::removeDatabase: connection 'MyConnection' is still in use, all queries will cease to work.
QSqlDatabasePrivate::addDatabase: duplicate connection name 'MyConnection', old connection removed.

There are mainly to classes namely MainWindow(Has database connection methods) and Dialog Following are my codes

MainWindow.h

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

public: QSqlDatabase mydb;
        bool conOpen(QString userName,QString password,QString hostname,int port,QString service){
            mydb=QSqlDatabase::addDatabase("QOCI","MyConnection");
            mydb.setUserName(userName);
            mydb.setPassword(password);
            mydb.setHostName(hostname);
            mydb.setPort(port);
            mydb.setDatabaseName(service);
            return mydb.open();

}

MainWindow.cpp

void MainWindow::on_pushButton_clicked()
{
    Dialog *dialog1 = new Dialog(this);
   if(conOpen(ui->uname->text(),ui->pword->text(),ui->ip->text(),ui->port->text().toInt(),ui->service->text())){

        dialog1->show();
}

Dialog.h

class Dialog : public QDialog
{
    Q_OBJECT

public:
    explicit Dialog(QWidget *parent = 0);
    ~Dialog();

private slots:
    void on_pushButton_clicked();

Dialog.cpp

void Dialog::on_pushButton_clicked()
{

    QSqlQueryModel *modal = new QSqlQueryModel();
    if(QSqlDatabase::contains("MyConnection")){

        QSqlQuery* qry=new QSqlQuery(QSqlDatabase::database("MyConnection"));
        qry->prepare("select NAME FROM Employees");
           qry->exec();
        modal->setQuery(*qry);
      ui->tableView->setModel(modal);

    }
}

The MainWindow form is used for login and Dialog form is used to retrieve entries in database table to a table view How can I correct the issue?

@HiI'mFrogatto yeah! I pressed the button in MainWindow several times but the problem is that dialog1 does not appear though I press the button :( — Kushan Peiris
– Kushan Peiris, Commented Sep 20, 2017 at 4:49
That's the problem. QSqlDatabase::addDatabase isn't meant to be called more that once. — frogatto
– frogatto, Commented Sep 20, 2017 at 4:50
yeah but why doesn't dialog1 appear when I click the button? :( — Kushan Peiris
– Kushan Peiris, Commented Sep 20, 2017 at 4:51
Have you tried to debug your program? Is dialog1->show(); called the first time? — m7913d
– m7913d, Commented Sep 21, 2017 at 8:31

frogatto · Accepted Answer · 2017-09-20 04:55:57Z

1

QSqlDatabase::addDatabase is a static function and every time you call it, it will create a connection instance. So if your app is designed to establish only a single connection to database server, you should not call it more that once.

QSqlDatabase QSqlDatabase::addDatabase(const QString &type, const QString &connectionName = QLatin1String( defaultConnection ))

Adds a database to the list of database connections using the driver type and the connection name connectionName. If there already exists a database connection called connectionName, that connection is removed.

You may need to move the logic of opening database code (including QSqlDatabase::addDatabase) to somewhere that gets called only once throughout the entire app.

edited Sep 20, 2017 at 4:55

answered Sep 20, 2017 at 4:54

frogatto

29.4k13 gold badges90 silver badges137 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Kushan Peiris Over a year ago

Thanx! The problem is dialog1 not appearing when I click the button! But why doen't it appear?

frogatto Over a year ago

@KushanPeiris Return value of conOpen may be false.

Collectives™ on Stack Overflow

QSqlDatabasePrivate::addDatabase: duplicate connection name 'MyConnection' error

1 Answer 1

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Related