#include <QApplication>
#include <QLCDNumber>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>
class Widget : public QWidget
{
    Q_OBJECT
public:
    explicit Widget(QWidget *parent = nullptr) :
        QWidget(parent)
    {
        auto layout = new QVBoxLayout(this);
        m_emitButton = new QPushButton("Emit Signal", this);
        layout->addWidget(m_emitButton);
        connect(m_emitButton, &QPushButton::clicked, this, &Widget::signalEmitted);
        auto reconnectButton = new QPushButton("Reconnect Signal", this);
        layout->addWidget(reconnectButton);
        connect(reconnectButton, &QPushButton::clicked, this, &Widget::reconnectSignal);
        m_counter = new QLCDNumber(this);
        layout->addWidget(m_counter);
    }
public slots:
    void reconnectSignal()
    {
        disconnect(m_emitButton, &QPushButton::clicked, this, &Widget::signalEmitted);
        connect(m_emitButton, SIGNAL(clicked()), this, SLOT(signalEmitted()));
    }
    void signalEmitted()
    {
        m_counter->display(m_counter->intValue() + 1);
    }
private:
    QPushButton *m_emitButton;
    QLCDNumber *m_counter;
};
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    Widget w;
    w.show();
    return app.exec();
}
#include "signal-slot.moc"