how to concatenate a variable with a string

[doforumda]

hi i am trying to concatenate a variable with a string. How can i do this?
here is the code

void login::show_user()
{
    QString user_name = user->text();
    QMessageBox::information(this, tr("Your Username"),
                             tr("Your username is user_name"));
}

void login::show_user()
{
    QString user_name = user->text();
    QMessageBox::information(this, tr("Your Username"),
                             tr("Your username is user_name"));
}

To copy to clipboard, switch view to plain text mode 

i want to concatenate user_name in QMessageBox to display username