Instantiate wrapper class from C++

Question

i have wrapped a simple c++ interface / class using pybind11

py::class_<IBaseObject, SmartPtr<IBaseObject>>(m, "BaseObject")
    .def(py::init([]()
    {
        return BaseObject_Create();
    }))
)

IBaseObject is interface, SmartPtr is custom holder type and BaseObject_Create is factory function which returns IBaseObject*.

Instatiating class from python works fine, however i also want to instantiate python wrapper class from C++ while passing IBaseObject* as parameter. Is this possible?

Note, sure, there seems to be code that can handle existing objects (check `init_instance`), but I don't know how it can be called (private function, but stored in other private implementationd etials as well). — Matthieu Brucher, Jan 21 '19 at 11:28

score 1 · Answer 1 · answered Mar 08 '19 at 13:53

If you just want to instantiate your class in your C++ binding code, you can use pybinds Python C++ Interface:

https://pybind11.readthedocs.io/en/stable/advanced/pycpp/object.html#calling-python-functions

Some ways to do this:

// Option 1: Use your existing class handle.
py::class_<IBaseObject, ...> py_cls(...);
py::object py_obj = py_cls();
// - Cast it if you need to.
auto* obj = py_obj.cast<IBaseObject*>();
// - or cast to `SmartPtr<IBaseObject>()` if its shareable.

// Option 2: Re-import elsewhere in your code.
py::object py_cls = py::module::import("my_pybind_module").attr("IBaseObject");
py::object py_obj = py_cls();
// - etc...

// Option 3: Use `eval` (blech)
py::module m = py::module::import("my_pybind_module");
py::object py_obj = py::eval("IBaseObject()", /* globals */ m.attr("__dict__"));

Instantiate wrapper class from C++

1 Answers1