void MainWindow::on_pushButton_clicked()
{
QObjectList q(ui->centralWidget->children());
for (int i = 0; i < q.length(); i++) {
QObject* o = q.at(i);
if (o->inherits("QPushButton")) {
QPushButton* b = qobject_cast<QPushButton*>(o);
b->setText("TEST");
};
}
}