[C++-sig] def_readwrite and custom rvalue converters

[Ralf W. Grosse-Kunstleve]

--- David Abrahams <dave at boost-consulting.com> wrote:
> > Is this still the best solution available?
> 
> Sorry, I don't remember enough about the problem to be able to say.

That strongly suggests the answer is "yes."

FWIW: Say you have a custom rvalue converter which converts Python tuples to
std::vector<int> and a to_python converter for the opposite direction.
Everything is fine for converting function arguments and return values.
However, with Boost 1.30.0 def_readonly() and def_readwrite() do not work for
that std::vector<int>. In connection with this you pointed me to the following
code:

data_members.cpp contains:

  // If it's a regular class type (not an object manager or other
  // type for which we have to_python specializations, use
  // return_internal_reference so that we can do things like
  //    x.y.z =  1
  // and get the right result.
  template <class T>
  struct default_getter_policy

You wrote further:

> Which selects a policy to use for getters.  The problem is that your
> converter can't use return_internal_reference, because it's making a
> list or tuple or something else which doesn't support weak references,
> instead of an extension class instance.

You told me that this can be used instead of def_readwrite():

      typedef return_value_policy<return_by_value> rbv;
      // ...
        .add_property("site", make_getter(&w_t::site, rbv()),
                              make_setter(&w_t::site))

You thought it would be better to handle this situation automatically with some
"not_exposed_as_class" specialization.

Ralf


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