#include <QObject>

class Model {
  private:
    double data;

  public:
    Model(double data) : data(data) {}
    double getData(void) const { return this->data; }

  signals:
    void dataChanged(double data);

  public slots:
    void setData(double data) {
      this->data = data;
      emit dataChanged(data);
    }
}

class GModel : public QObject, public Model{
  public:
    GModel(double data) : Model(data) {}
}