Hello,
Classes with protected destructors (as found when custom reference
counting is used) seem to cause some trouble when using bp::wrapper<>
containing a method that takes a const reference to a refcounted class.
Say I have:
#include <cstdio>
#include <boost/python.hpp>
namespace bp = boost::python;
class Thing
{
protected:
virtual ~Thing() {}
};
class Callback
{
public:
Callback() { }
virtual void execute(const Thing& t) { }
protected:
virtual ~Callback() {}
};
And I want to add a wrapper class so that Callback can be derived from
in Python and its execute() method overridden.
Simply writing
struct CallbackWrap : Callback, bp::wrapper<Callback>
{
void execute(const Thing& t)
{
if (bp::override ovr = this->get_override("execute"))
{
fprintf(stderr, "have override, calling...\n");
ovr(t);
fprintf(stderr, "done calling\n");
}
else
Callback::execute(t);
}
void default_execute(const Thing& t)
{
fprintf(stderr, "default\n");
this->Callback::execute(t);
}
};
BOOST_PYTHON_MODULE(doh)
{
bp::class_<Thing, boost::noncopyable>("Thing")
;
bp::class_<CallbackWrap, boost::noncopyable>("Callback")
.def("execute", &Callback::execute, &CallbackWrap::default_execute)
;
}
doesn't cut it as I get a compile error due to Thing::~Thing() being
protected.
I've found in the archive the trick you can use to wrap a normal method
taking a const reference, e.g.
void
Callback_execute(Callback& self, Thing& t)
{
// Work around the const Thing& parameter
self.execute(t);
}
bp::class_<Callback>("Callback")
.dep("execute", &Callback_execute)
;
But I don't see how I can use that in the case of the wrapper class. I
tried adding functions that do the equivalent thing but for method
Callback::execute() and CallbackWrap::default_execute() but that doesn't
compile. And I can't find in the documentation of class_<>::def() the
exact requirements for the special case of .def() that is used when the
extra default implementation is specified.
Is there a way to get wrapper classes to work in this situation?
Thanks,
Paul
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