Как вариант:
Класс вторичной формы.
#include <QPushButton>
class MyForm:
public QWidget
{
Q_OBJECT
public:
MyForm(QObject * parent = 0);
public slots:
void HideButton();
private:
QPushButton * button;
};
MyForm::MyForm(QObject * parent):
QWidget(parent)
{
QPushButton * button = new QPushButton(this);
}
void MyForm::HideButton()
{
button->setVisible(false);
}
Класс главного окна.
#include <QMainWindow>
class MainWindow:
public QMainWindow
{
Q_OBJECT
public:
MainWindow();
};
MainWindow::MainWindow()
{
QPushButton * button = new QPushButton(this);
MyForm * myForm = new MyForm(this);
connect(button, SIGNAL(clicked()), myForm, SLOT(HideButton()));
}