QObject与其的派生类之间的转换？该如何处理

QObject与其的派生类之间的转换？
有这么一个类：

C/C++ code

//a.hclass A :public QObject{       Q_OBJECT       public:          A(QObject *parent=0);          void fun1();          void fun2();      private:            int x;            int y;};//a.cppA::A(QObject *parent):QObject(parent),x(1),y(2){}void A::fun1(){        A  a=*this; //这么搞会出现错误：QObject::QObject(const QObject&)是私有的        a.fun2();}void A::fun2() {.....}

C/C++ code

A(const A& a)    {        x = a.x;        y = a.y;    }