Build problems when adding `__str__` method to Boost Python C++ class
- by Rickard
I have started to play around with boost python a bit and ran into a problem. I tried to expose a C++ class to python which posed no problems. But I can't seem to manage to implement the __str__ functionality for the class without getting build errors I don't understand.
I'm using boost 1_42 prebuild by boostpro. I build the library using cmake and the vs2010 compiler.
I have a very simple setup. The header-file (tutorial.h) looks like the following:
#include <iostream>
namespace TestBoostPython{
class TestClass {
private:
double m_x;
public:
TestClass(double x);
double Get_x() const;
void Set_x(double x);
};
std::ostream &operator<<(std::ostream &ostr, const TestClass &ts);
};
and the corresponding cpp-file looks like:
#include <boost/python.hpp>
#include "tutorial.h"
using namespace TestBoostPython;
TestClass::TestClass(double x)
{
m_x = x;
}
double TestClass::Get_x() const
{
return m_x;
}
void TestClass::Set_x(double x)
{
m_x = x;
}
std::ostream &operator<<(std::ostream &ostr, TestClass &ts)
{
ostr << ts.Get_x() << "\n";
return ostr;
}
BOOST_PYTHON_MODULE(testme)
{
using namespace boost::python;
class_<TestClass>("TestClass", init<double>())
.add_property("x", &TestClass::Get_x, &TestClass::Set_x)
.def(str(self))
;
}
The CMakeLists.txt looks like the following:
CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
project (testme)
FIND_PACKAGE( Boost REQUIRED )
FIND_PACKAGE( Boost COMPONENTS python REQUIRED )
FIND_PACKAGE( PythonLibs REQUIRED )
set(Boost_USE_STATIC_LIBS OFF)
set(Boost_USE_MULTITHREAD ON)
INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})
INCLUDE_DIRECTORIES ( ${PYTHON_INCLUDE_PATH} )
add_library(testme SHARED tutorial.cpp)
target_link_libraries(testme ${Boost_PYTHON_LIBRARY})
target_link_libraries(testme ${PYTHON_LIBRARY}
The build error I get is the following:
Compiling...
tutorial.cpp
C:\Program Files (x86)\boost\boost_1_42\boost/python/def_visitor.hpp(31) : error C2780: 'void boost::python::api::object_operators::visit(ClassT &,const char *,const boost::python::detail::def_helper &) const' : expects 3 arguments - 1 provided
with
[
U=boost::python::api::object
]
C:\Program Files (x86)\boost\boost_1_42\boost/python/object_core.hpp(203) : see declaration of 'boost::python::api::object_operators::visit'
with
[
U=boost::python::api::object
]
C:\Program Files (x86)\boost\boost_1_42\boost/python/def_visitor.hpp(67) : see reference to function template instantiation 'void boost::python::def_visitor_access::visit,classT>(const V &,classT &)' being compiled
with
[
DerivedVisitor=boost::python::api::object,
classT=boost::python::class_,
V=boost::python::def_visitor
]
C:\Program Files (x86)\boost\boost_1_42\boost/python/class.hpp(225) : see reference to function template instantiation 'void boost::python::def_visitor::visit>(classT &) const' being compiled
with
[
DerivedVisitor=boost::python::api::object,
W=TestBoostPython::TestClass,
classT=boost::python::class_
]
.\tutorial.cpp(29) : see reference to function template instantiation 'boost::python::class_ &boost::python::class_::def(const boost::python::def_visitor &)' being compiled
with
[
W=TestBoostPython::TestClass,
U=boost::python::api::object,
DerivedVisitor=boost::python::api::object
]
Does anyone have any idea on what went wrrong? If I remove the .def(str(self)) part from the wrapper code, everything compiles fine and the class is usable from python. I'd be very greatful for assistance.
Thank you,
Rickard
