On 02/02/2012 09:30 AM, Holger Brandsmeier wrote:
Dear list,
how can I combine make_constructor() and BOOST_PYTHON_FUNCTION_OVERLOADS()?
I have a static member function in a class that "acts like a
constructors", in the sense that it returns a shared pointer to the
class. The function has default arguments, thats why I was thinking of
using BOOST_PYTHON_FUNCTION_OVERLOADS.
For usual member functions I've been using it like this:
BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS(Operator_apply, apply, 2, 5)
[...]
.def("apply",&ClassT::apply, Operator_apply() )
So for the constructor I thought probably I should use it like
BOOST_PYTHON_FUNCTION_OVERLOADS(fPfemSpace_create, create, 2, 3)
[...]
.def("__init__", make_constructor(&ClassT::create ),
fPfemSpace_create())
but that fails with the error:
/usr/include/boost/python/class.hpp:598:37: error: no matching
function for call to 'get_signature'
name, overloads, *this, detail::get_signature(sig));
I tried out a few other variations for ".def(" but I didn't find the
right one yet. Is there a way to combine make_constructor with
BOOST_PYTHON_FUNCTION_OVERLOADS?
I've always used arg lists rather than the OVERLOADS macros to deal with
default arguments, and I can confirm that those work with make_constructor:
bp::make_construct(&ClassT::create, bp::default_call_policies(),
(bp::arg("a"), bp::arg(b")=0))
The advantage is that your Python users get to use keyword args; the
disadvantage is that you have to write them out (along with the default
value).
I have noticed, however, that make_constructor isn't as flexible as
make_function about the order of its own optional arguments - if you
want to pass args, you also have to pass default_call_policies as the
second argument, as I did above. The same trick might work for the
OVERLOADS macros, if you'd prefer to use those.
Jim
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