[C++-sig] Inherited instance variables

[Matt Giger]

Hi, I just discovered Boost.Python and I am very impressed (as I am 
with most of Boost). I have embedded a Python interpreter in my 
project and would like to tie in some C++ classes but am having 
problems with inherited member variables.

Here is my example:

C++
---

struct foo {
   foo(void) {}
   virtual ~foo(void) {}
   virtual bool handle_evt(object event) { return false; }
   list children;
}

struct foowrap : foo {
   foowrap(PyObject* self) : self_(self) {}
   foowrap(PyObject* self, const foo& f) : foo(f), self_(self) {}
   bool handle_evt(object event)
    { return call_method<bool>(self_, "handle_evt", event); }
   static bool def_handle_evt(foo* f, object event)
    { return f->foo::handle_evt(event); }
   PyObject* const self_;
};

BOOST_PYTHON_MODULE(foomod)
{
   class<foo, foowrap>("foo")
    .def("handle_evt", &foowrap::def_handle_evt)
    .def_readwrite("children", &widget::children);
}


Python
------

import foomod
class subfoo(foomod.foo):
   def __init__(self, parent):
     self.parent = parent
     self.parent.children.append(self)
   def __del__(self)
     self.parent.children.remove(self)
   def handle_evt(self, event)
     print event
     for child in children:
       if handle_evt(event)
         return true
     else
       return false

f = foo()      # works fine
g = subfoo(f)  # works fine
h = subfoo(g)  # breaks

Error:
self.parent.children.append(self)
TypeError: bad argument type for built-in operation


# no children list available in the subfoo class instance 'g'
print g.children
TypeError: bad argument type for built-in operation

It appears that the children list object is not visible from any 
subclasses of the foo class.

I have tried changing the line:
    .def_readwrite("children", &widget::children)

with

     .add_property("children",
       make_getter(&foo::children, return_internal_reference<>()),
       make_setter(&foo::children))

but still no luck...any help would be appreciated, thanks.

-- 
Matt Giger
Lunar Software, Inc.
mgiger at lunarsoft.com