Try the following:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
AddSlotsToGroup();
}
void MainWindow::AddSlotsToGroup()
{
QButtonGroup* group = new QButtonGroup(this);
group->addButton(ui->slot_0);
group->addButton(ui->slot_1);
//...
connect(group, SIGNAL(buttonClicked(int)),
this, SLOT(onGroupButtonClicked(int)));
}
By the way, you need to learn C++ first to master Qt.