Jim, how do you handle smart_ptr<const T> in boost python? Do you simply cast away the constness?
For my custom smart pointer I provide a class extending to_python_converter<Teuchos::RCP<T>, rcp_to_python<T>, true> now I decided to also implement to_python_converter<Teuchos::RCP<const T>, rcp_to_python_const<T>, true> where I simply cast away the constness and use the above implementation. This seems to be working so far. Did you provide a smarter implementation for shared_ptr<const T>? -Holger On Wed, Oct 5, 2011 at 15:44, Jim Bosch <tallji...@gmail.com> wrote: > On 10/05/2011 03:08 AM, Holger Brandsmeier wrote: >> >> Dear list, >> >> how should I export functions to python which return smart pointers to >> const-pointers, e.g. shared_ptr<const T>? >> >> For my own classes I always tried to avoid this problem by always >> providing a methods which returns shared_ptr<T>. >> >> Now I need to export the following method in a class provided by some >> other software package (Trilinos). Its implementation I do not want to >> change, the function is declared as >> Teuchos::RCP< const Teuchos::Comm< int> > getComm () const >> (if you need details: >> >> http://trilinos.sandia.gov/packages/docs/r10.6/packages/tpetra/doc/html/classTpetra_1_1MpiPlatform.html >> ) >> >> I believe I already exported the custom smart pointer `Teuchos::RCP` >> to python, I also exported the class `Teuchos::Comm< int>` to python, >> but I get the error >> No to_python (by-value) converter found for C++ type: >> Teuchos::RCP<Teuchos::Comm<int> const> >> which is perfectly true, as I did not export the class `const >> Teuchos::Comm<int>`. >> >> I briefly tried to export also the const version of this class (all >> methods that I need are provided are available for the const version), >> but I failed exporting the class with varying error message, depending >> on how I tried to export it. I realized that I don't know how or even >> if I should export a const version of a type? >> >> Is there another workaround to this problem? Is there something I'm >> missing in the implementation of my custom smart pointer? >> >> I could wrap the function getComm() above to cast away the const'ness, >> but do I need to? >> >> I also found some old messages on the list titled "[Boost.Python] >> shared_ptr<const T>" with some workaround proposed by providing >> get_pointer for const T, but I believe that I have a different problem >> that I can not solve by modifying get_pointer. >> > > I'm afraid you do have a different problem, though some of those ideas help. > Essentially, Boost.Python's support for custom smart pointers isn't as > complete as its support for shared_ptr, and its support for const smart > pointers is basically nonexistent. You're pretty much in > not-currently-supported territory. > > I think wrapping getComm() to cast away the constness is going to be the > easiest way to make this work, but if you have many such functions it may be > worth digging deeper into the Boost.Python internals to try and trick it > into working by specializing some templates. > > Jim > _______________________________________________ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > http://mail.python.org/mailman/listinfo/cplusplus-sig > _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
