deferred_declaration_cython

_myheader.pyx

# -*- coding: utf-8 -*-
# distutils: language = c++

from libcpp cimport bool

cdef extern from "myheader.hpp":
    cdef cppclass MyInt:
        void add_two()
        bool is_poitive()

    cdef cppclass MyFloat:
        void add_two()
        bool is_poitive()


cdef class PyBase:
    cdef void * thisptr;

    def add_two(self):
        self.thisptr.add_two()

    def is_poitive(self):
        return self.thisptr.is_poitive()

# Is it possible to define "add_two" and "is_positive" only in PyBase?
# or do I need to have copies of these methods in each cdef class below?


cdef class PyMyInt(PyBase):

    def __cinit__(self, int val):
        self.thisptr = <void *>(new MyInt(val))

    def __dealloc__(self):
        del self.thisptr


cdef class PyMyFloat(PyBase):

    def __cinit__(self, double val):
        self.thisptr = <void *>(new MyFloat(val))

    def __dealloc__(self):
        del self.thisptr


def run():
    a = PyMyInt(-1)
    print(a.is_poitive())
    a.add_two()
    print(a.is_poitive())

    b = PyMyFloat(-2.0)
    print(b.is_poitive())
    b.add_two()
    print(b.is_poitive())

myheader.hpp

template<typename T>
class Base {
    T value;
    Base(T val) : value(val) {}
    void add_two() {
        this->value *= 2;
    }
    bool is_positive() {
        return this->value >= 0;
    }
};

class MyInt : public Base<int> {
    MyInt(int val) : Base(val) {}
};

class MyFloat : public Base<double> {
    MyFloat(double val) : Base(val) {}
}

setup.py

from distutils.core import setup
from Cython.Build import cythonize
setup(
    ext_modules = cythonize("_myheader.pyx", gdb_debug=True)
)