[C++-sig] NoProxy and the data in an std::map

[Noah Schwartz]

On Thursday 19 October 2006 15:00, Roman Yakovenko wrote:
> On 10/19/06, Noah Schwartz <noah.schwartz1 at gmail.com> wrote:
> > Hi,
> >
> >         I am having another issue with the indexing suite. I have an
> > std::map from int to boost::shared_ptr<MyClass>. However, in python, I
> > can't seem to look at the data element of an iterator into that map. I
> > get a TypeError complaining that there is no class registered for C++
> > class
> > boost::shared_ptr<MyClass>. However, I did tell python about shared_ptrs
> > of MyClass and no_proxy is set to true.
> >
> > Binding code:
> > #include <boost/python.hpp>
> > #include <boost/python/suite/indexing/map_indexing_suite.hpp>
> > #include <boost/python/register_ptr_to_python.hpp>
> > using namespace boost::python;
> >
> > #include <map>
> >
> > class MyClass {
> > public:
> >         int e;
> > };
> >
> > class MyClassMaker {
> > public:
> >         std::map<int, boost::shared_ptr<MyClass> > & func() {return
> > myMap;}; void add(int x, int y) {boost::shared_ptr<MyClass> instance(new
> > MyClass); instance->e = y; myMap[x] = instance;};
> >
> >         std::map<int, boost::shared_ptr<MyClass> > myMap;
> > };
> >
> > BOOST_PYTHON_MODULE(testlib)
> > {
> >         class_<MyClass, boost::shared_ptr<MyClass> >("MyClass")
> >                 ;
> >         class_<MyClassMaker>("MyClassMaker")
> >                 .def("func", &MyClassMaker::func,
> > return_value_policy<copy_non_const_reference>())
> >                 .def("add", &MyClassMaker::add)
> >                 ;
> >
> >         class_<std::map<int, boost::shared_ptr<MyClass> >
> > >("MapIntMyClass") .def(map_indexing_suite<std::map<int,
> > boost::shared_ptr<MyClass> >, true>()) ;
> > }
> >
> > Python code:
> > >>> import testlib
> > >>>
> > >>> a = testlib.MyClassMaker()
> > >>>
> > >>> a.add(1, 2)
> > >>> a.add(3, 4)
> > >>> a.add(5, 6)
> > >>>
> > >>> map = a.func()
> > >>>
> > >>> for i in map:
> >
> > ...     print i.key()
> > ...     print i.data()
> > ...
> > 1
> > Traceback (most recent call last):
> >   File "<stdin>", line 3, in ?
> > TypeError: No Python class registered for C++ class
> > boost::shared_ptr<MyClass>
> >
> > If you look at the binding code I have specified shared_ptr as a held
> > type.
> >
> > I should mention that if I use a simpler container such as a vector
> > container of shared_ptr's and do not specify no_proxy to true then I get
> > the same error. Maybe the no_proxy code isnt being properly applied to
> > the second template type in the map container.
>
> Google is your friend:
>
> http://mail.python.org/pipermail/c++-sig/2005-November/009849.html
> http://mail.python.org/pipermail/c++-sig/2005-November/009854.html

I did see this before sending the e-mail. That thread is almost a year old and 
the original sender was using boost 1.33.0. Are you telling me the fix made 
last year is still in CVS and isn't part of 1.33.1?


Noah