Can not cast into the derived class from QScrollBar

[learning_qt]

I defined a class ViewScrollBar derived from QScrollBar. There is also a public slot: void currentValue(i nt value); I hope to use this slot in another class.

#include <QScrollBar>
class ViewScrollBar: public QScrollBar
{
 Q_OBJECT
public:
    ViewScrollBar();
    ~ViewScrollBar();
    int getCurrentValue();
 
public slots:
   void currentValue(i nt value);
 
private:
    int currentPos;
};

#include <QScrollBar>
class ViewScrollBar: public QScrollBar
{
 Q_OBJECT
public:
    ViewScrollBar();
    ~ViewScrollBar();
    int getCurrentValue();
    
public slots:
   void currentValue(i nt value);

private:
    int currentPos;
};

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Then I get the scroll bar from the QGraphicsView by the method:
ViewScrollBar *hScrollBar=static_cast<ViewScrollBar*>(graphicsVi ew->horizontalScrollBar());

I connect the signal valueChanged() from QScrollBar with my public slot currentValue(i nt value) in ViewScrollBar class.
connect(hScrollBar, SIGNAL(valueChanged(int)),hScrollBar, SLOT(currentValue(int)));

when I run, there is always warning that:
Object::connect: No such slot QScrollBar::currentValue(int).
The object hScrollBar is ViewScrollBar now. But it is still regarded as its parent class. How can cast it from QScrollBar to ViewScrollBar?