Qsqlite duplicate connection warning in qt c++ - c++

Question

I am creating an application in qt which uses sqlite database. I have written a class to open database connection. The constructor for the class is given below:
currencydb::currencydb()
{
currency = QSqlDatabase::addDatabase("QSQLITE");
currency.setDatabaseName("currency.sqlite");
if(!currency.isOpen())
{
if (!currency.open())
{
qDebug() << "Error: connection with database fail";
}
else
{
qDebug() << "Database currency: connection ok";
}
}
}
Since i use this constructor, when i create object for the database class, i get following warning:
QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.
Is there a way to check whether the database is already open?

Answer 1

That warning doesn't mean that your database is already open but that you already have a connection to the database with a default name. The connection provides access to the database via (in your case SQLITE v3) database driver. You create a default connection to the database when you don't pass the connection name argument when you call static public method QSqlDatabase::addDatabase().
You can use QSqlDatabase::contains() for checking if you already have the default connection.
CurrencyDb::CurrencyDb()
{
currency = openDb("QSQLITE", "currency.sqlite");
}
QSqlDatabase CurrencyDb::openDb(const QString &driver, const QString &name) const
{
QSqlDatabase db;
// contains() default argument is initialized to default connection
if (QSqlDatabase::contains())
{
db = QSqlDatabase::database(QLatin1String(QSqlDatabase::defaultConnection), false);
}
else
{
db = QSqlDatabase::addDatabase(driver.toUpper());
}
db.setDatabaseName(name);
if (!db.isValid())
{
// Log error (last error: db.lastError().text()) and throw exception
}
if (!db.open())
{
// Log error (last error: db.lastError().text()) and throw exception
}
return db;
}