On 02/03/2012 03:13 PM, Holger Brandsmeier wrote:
Dear list,how can I have a static member function that acts like a constructor in a Wrapper, i.e. I have a class that I want to extend from python? I have a wrapper class around a class (PfemSpace) that has this static member functions: static RCP<PfemSpaceWrapperT> create( ... ) { RCP<PfemSpaceWrapperT> ret(new PfemSpaceWrapperT( ... )); ret->setThisRCP(ret); return ret; } This method is exported via .def("__init__", make_constructor(&ClassWrapperT::create ) ) This works without errors, but when I use this from python via class PfemSpaceStaticCond(PfemSpace): def __init__(self, ...): super(PfemSpaceStaticCond, self).__init__(...) def visit_createFemData(self): print '## [PfemSpaceStaticCond_init] visit_createFemData' Here I call the constructor that I exported via make_constructor in __init__(). Unfortunately the member function visit_createFemData that I override in python never gets called. When I use a "real" constructor instead of the one exported via make_constructor() then the function visit_createFemData gets called. I assume the error is somewhere that with a real constructor boost::python can call an inplace constructor, while with my make_constructor it can't. Is there some way to have the needed functionality with make_constructor? Note: today I came to the conclusion that I a read constructor instead of a static member function is not an option for me due to the issues I wrote in my previous mail "storing weak_ptr to this in classes extended from python". That previous mail is actually from yesterday, but it originally got rejected because I send it from a wrong email address, so I'm sorry that you are receiving two mails from me today. For a moment I was very happy that this "static constructor-like function in the Wrapper class" would solve all my problems, but I am still missing something.
I'm hoping my reply to your other email may give you a way forward, because I think there's a possibility that you've run into a real limitation of Boost.Python here.
The only thing I can think of is to override __new__, and not override __init__; that might get the make_constructor version called.
But I'm just guessing. make_constructor, useful as it is, just doesn't seem to really have the polish the rest of Boost.Python has, and I wouldn't be surprised if it just doesn't work here. After all, if you're wrapping a function that returns a smart pointer, there's no guarantee that contains an instance of the wrapper class needed to support Python-side polymorphism rather than just an instance of the C++ base class.
Jim _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
