[C++-sig] Re: Problem With Calling Methods on Python Subclasses from C++

[David Abrahams]

Mark Rowe <lists.python.org at bdash.net.nz> writes:

> class _ErrorHandlerWrapper : public ErrorHandler, public wrapper<ErrorHandler>
> {
>     public:
>         virtual void handleError(const Error & err) const {
>             if (override f = this->get_override("handleError"))
>             {
>                 f(err);

If you want the type of err to be preserved, you have to pass it by
reference:

                  f(boost::ref(f));

>             }
>             else
>                 ErrorHandler::handleError(err);
>         }
> };

Boost.Python never passes anything by reference, by default, because
it's unsafe: it can lead to dangling pointers.  It would be very
interesting to consider copying and passing whole most-derived class
instances by value, but that's not implemented.

HTH,
-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com