QPointer gives compilation errors.

[pkj]

I have class B inheriting Class A which in turn inherits QObject.

class A: public QObject{
Q_OBJECT
...
};
class B: public A{
Q_OBJECT
...
};

class A: public QObject{
Q_OBJECT
...
};
class B: public A{
Q_OBJECT
...
};

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At some place I instantiate class B. At some other place I want to use Class B pointer. To avoid dangling pointer, QPointer looked very interesting. So while storing the pointer of class B, I used QPointer<B> bptr
But bptr = bClassInstancePtr gives compilation errors like cannot convert from B* to QObject* . What am I doing wrong?