On May 8, 2013, at 23:58 , Jim Bosch <[email protected]> wrote:
> On 05/08/2013 05:48 PM, Jim Bosch wrote:
>> On 05/08/2013 04:33 PM, Wichert Akkerman wrote:
>>> I am trying to expose a class with a boost::uuids::uuid member to Python.
>>> The class is pretty simple:
>>>
>>> class Article {
>>> public:
>>> boost::uuids::uuid uuid;
>>> };
>>>
>>> which is exposed like this:
>>>
>>> article
>>> .def(init<boost::uuids::uuid, Article::Type>((arg("uuid")))
>>> .def_readwrite("uuid", &Article::uuid);
>>>
>>> and I have basic converter registered (see
>>> https://gist.github.com/wichert/5543390 , it is a bit large to include in
>>> this email). This compiles fine and the uuid convertor works correctly when
>>> trying converting from python to C++, but trying to access the uuid
>>> property results in "TypeError: No Python class registered for C++ class
>>> boost::uuids::uuid". I don't understand why that doesn't work; does anyone
>>> see what I missed?
>>>
>>
>> I suspect that def_readwrite requires lvalue converters, and I see that
>> you've only implemented an rvalue converter. I think in this case you're
>> better off just writing a getter and setter, and wrapping those using
>> add_property.
>>
>
> Ah, sorry, that didn't make any sense. There's no such thing as an lvalue
> to-Python converter, and to-Python is the problem here.
>
> You may want to try also registering your to-Python converter for the
> pointers and/or references to uuid. I ran into a similar problem with
> getting def_readwrite to work a while back, and specializing for
> pointer/reference/const variants made it go away, though I was using a
> different converter mechanism (by partial specialization of some template
> classes - not something I'd recommend here).
If I try to do that by adding this:
to_python_converter<boost::uuids::uuid, uuid_to_python>();
to_python_converter<boost::uuids::uuid&, uuid_to_python>()
I get a compile error:
/opt/local/include/boost/python/converter/as_to_python_function.hpp:21:84:
error: 'type name' declared as a pointer to a reference of type
'boost::uuids::uuid &'
static void convert_function_must_take_value_or_const_reference(U(*)(T),
int, T* = 0) {}
^
/opt/local/include/boost/python/to_python_converter.hpp:88:10: note: in
instantiation of template class
'boost::python::converter::as_to_python_function<boost::uuids::uuid &,
<anonymous>::uuid_to_python>' requested here
&normalized::convert
^
../../python/uuid.cc:77:2: note: in instantiation of member function
'boost::python::to_python_converter<boost::uuids::uuid &,
<anonymous>::uuid_to_python, false>::to_python_converter' requested
here
python::to_python_converter<boost::uuids::uuid&, uuid_to_python>();
which suggests that to_python_converter doesn't really like to see references.
Wichert.
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