Qsqlite duplicate connection warning in qt c++

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 in the constructor whether the database is already open?