On 07/30/2011 01:15 PM, Valentin Perrelle wrote:
Hi,
I'm currently embedding and extending Python using Boost.Python. I'm
trying to expose some c++ library (OIS) classes to my Python scripts.
This library mainly exposes abstract classes since the actual
implementation are derived classes specialized for each operating system.
So, i have to wrap those abstract classes. Then, eventually i will
convert some existing C++ object of this class to its Python equivalent.
Ideally, I would think that the HeldType is a pointer to the existing
C++ object. There is no pointer managment problem since the lifetime of
the object is greater than the execution time of the script.
In this case, I don't you need to specify a HeldType, because that only
affects what happens when you construct the object in Python, and you
aren't every doing that. But you do need to specify "noncopyable" if
the class doesn't have a copy constructor...
There is probably something i don't understand in the design of
Boost.Python. At this point, my problem is that i need a to_python
conversion which requires the abscence of noncopyable attribute which
then implies to be able to build an instance of the object (which i
cannot provide since the class is abstract, and i don't have any
concrete derived class). I don't yet understand why holding a pointer in
the Python object requires the ability to build instances of the wrapped
class. The exact compile-time error i get is:
boost_1_44/boost/python/object/pointer_holder.hpp:194:14: error: cannot
allocate an object of abstract type 'OIS::Keyboard'
Why do you think you can't have noncopyable? You can certainly support
some to-python conversions (including the one you've invoked below with
"ptr(keyboard)") on a noncopyable class. Are you hoping to support some
specific one, or is this the root of your misunderstanding?
Anyhow, I'd recommend trying
class_<Keyboard, noncopyable>("Keyboard", no_init);
with the rest of what you have.
Good luck!
Jim Bosch
BOOST_PYTHON_MODULE(OIS)
{
class_<Keyboard, Keyboard*>("Keyboard", no_init);
}
Python init:
try {
PyImport_AppendInittab("OIS", PyInit_OIS);
Py_InitializeEx(0);
object main(import("__main__"));
dict globals(main.attr("__dict__"));
globals["keyboard"] = ptr(keyboard);
}
catch (error_already_set&) {
PyErr_Print();
}
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