Same database connection for multiple forms

[Lasith]

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I am creating a simple qt application to provide details and login to the application and retrieve details from the database.It has mainly 2 forms(MainWindow and Dialog) A DBconncetion class has been written to obtain a database connection! I used the DBconnection class to log into application by giving details via the MainWindow form! but I don't know how to keep the connection that I opened in the MainWindow form and use it to retreive the data to the tableview in the Dialog form.

mycode is as follows

DBconnection.h (working successfully)

public:
QSqlDatabase mydb;
bool connOpen(QString uname,QString pword,QString ip,int port,QString dbname){
mydb=QSqlDatabase::addDatabase("QOCI","MyDB");
mydb.setUserName(uname);
mydb.setPassword(pword);
mydb.setHostName(ip);
mydb.setPort(port);
mydb.setDatabaseName(dbname);
mydb.open();
return true;

    }

MainWindow.cpp (working successfully)

void MainWindow::on_pushButton_clicked()
{
DBconnection con;
if(con.connOpen(ui->lineEdit->text(),ui->lineEdit_2->text(),ui->lineEdit_3->text(),ui->lineEdit_4->text().toInt(),ui->lineEdit_5->text())){
Dialog dialog1;

        dialog1.setModal(true);
        dialog1.exec();

    }

}

Dialog.cpp (not working)

void Dialog::on_pushButton_clicked()
{
QSqlQueryModel *modal = new QSqlQueryModel();
con.connOpen();

QSqlQuery* qry=new QSqlQuery(con.mydb);


qry->prepare("select NAME FROM TEST1");
   qry->exec();
   modal->setQuery(*qry);
   ui->tableView->setModel(modal);

}

How can I adjust my code so that I can retrieve data to the tablewidget in Dialog form from the connection I made from the MainWindow form?

[Locked as duplicate of https://forum.qt.io/topic/83309/connecting-to-database-when-a-form-loads-using-signals-and-slots ~kshegunov]

[jsulm]

@Lasith Just call http://doc.qt.io/qt-5/qsqldatabase.html#database and pass the name of your connection as parameter ("MyDB" in your example).