Pimpl implemenation - compilation error on static_cast base* to Derieved*

[sunil.thaha]

Is this very simple that no one want to answer ? or

[spud]

You can't define the function there, since at that point the compiler doesn't know that QstObjectPrivate inherits PrivateData you have to implement it at the end of the file:

...
class QstObject : public PublicInterface
{
public:
	QstObject();
private:
	inline QstObjectPrivate* data_pointer_test();
};
 
class QstObjectPrivate : public PrivateData
{
public:
	QstObjectPrivate( PublicInterface *iface )
		: PrivateData( iface )
	{
	}
};
 
QstObject::QstObject()
	: PublicInterface( new QstObjectPrivate(this) )
{
}
 
QstObjectPrivate* QstObject::data_pointer_test()
{
	return static_cast<QstObjectPrivate*>( _data );
}
...

...
class QstObject : public PublicInterface
{
public:
	QstObject();
private:
	inline QstObjectPrivate* data_pointer_test();
};

class QstObjectPrivate : public PrivateData
{
public:
	QstObjectPrivate( PublicInterface *iface )
		: PrivateData( iface )
	{
	}
};

QstObject::QstObject()
	: PublicInterface( new QstObjectPrivate(this) )
{
}

QstObjectPrivate* QstObject::data_pointer_test()
{
	return static_cast<QstObjectPrivate*>( _data );
}
...

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[sunil.thaha]

Thanks a lot !!
and that helped me make sense of why Qt's pimpl implementation uses reinterpret cast