On 08/16/2010 02:33 PM, Branan Purvine-Riley wrote:
I'm working on replacing hand-rolled python bindings with boost.python.
Unfortunately, I've hit a bit of a snag at a particular construct:
a = someFunction(...) # returns an instance of myClass
b = myClass(a)
In the current bindings, this creates a new python object that references the
same internal C++ object. It's effectively no-op, and I have no idea why it was
written that way in the first place, but I have to maintain API compatibility.
That being the case, how do I implement this in boost.python? I considered
replacing __init__, but it seems if I implement that as a standalone function
rather than a constructor, boost has already created a new C++ instance for
me, so that's too late. I'm not really sure what else to try.
You'll want to use the make_constructor function; this takes a C++
function returning a C++ smart pointer and creates a Python __init__
overload.
I *think* this should work (I haven't tested it):
----------------------------------------------
boost::shared_ptr<MyClass> construct(boost::python::object const & arg) {
return boost::python::extract< boost::shared_ptr<MyClass> >(arg);
}
BOOST_PYTHON_MODULE(example) {
boost::python::class_<MyClass>("MyClass")
.def("__init__", boost::python::make_constructor(&construct))
;
boost::python::register_ptr_to_python<
boost::shared_ptr<MyClass>
>();
}
----------------------------------------------
Hope that helps.
Jim Bosch
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