David Abrahams schrieb:

on Mon Jun 04 2007, Alexander Eisenhuth <newsuser-AT-stacom-software.de> wrote:

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How to wrap methode Get with Boost.Python?

First, I suggest you take your question to the C++-sig (http://www.boost.org/more/mailing_lists.htm#cplussig).

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class MyClass { public: MyClass();

void GetX(double &pos_x); [...]

I'v tried it with:

.def( "GetX" , &::MyClass::GetX , bp::arg("") , bp::return_value_policy<bp::return_arg<1>() >()

But when I try it in python:

Boost.Python.ArgumentError: Python argument types in MyClass.GetX(MyClass, int) did not match C++ signature: GetX(class MyClass::LedPosition_C {lvalue}, int {lvalue} )

Any ideas?

return_value_policy is only good for telling Boost.Python how to handle the actual (non-void) return value of your C++ function. In your case, create a thin wrapper function:

Ok, thanks for that hint.

double GetX2(MyClass& self, double pos_x) { self.GetX(pos_x); return pos_x; }

and wrap that instead of GetX:

.def("GetX", GetX2)

So boost.python doesn't have a mechanism to transform in the wrapper code a call by reference into return value?