Binding nested subclasses in pybind11

nested_pybind.cpp

#include <pybind11/stl.h>
#include <pybind11/pybind11.h>
#include <pybind11/operators.h>

namespace py = pybind11;
using namespace pybind11::literals;
using namespace std;

template<typename T>
class Property{
public:
  virtual ~Property(){}
  virtual Property& operator= (const T& f){ value = f; return *this;}
  virtual const T& operator () () const {return value;}
  virtual explicit operator const T& () const {return value;}
  virtual T* operator->() {return &value;}
protected:
  T value;
};

class Test {
public:
  Test() { someProperty = 1.; }
  class NestedProperty: public Property<float>{
  public:
    virtual NestedProperty& operator= (const double &f){
      value = f; return *this;
    }
  };
  NestedProperty someProperty;
};

PYBIND11_MODULE(example, m) {
  py::class_<Test>(m, "Test")
    .def(py::init<>())
    .def_property("someProperty",
                  [](const Test &self) { return static_cast<float>(self.someProperty); },
                  [](Test &self, float value) { self.someProperty = value; });
}

Usage from python

The class is part of a bigger project that runs in C++. There are some properties that need to be set with internal logic. I prefer to keep the setter getter logic on the c++ side and allow python to interface with it. The problem is that I don't know how to provide these bindings through pybind11.

from nest_cppclass import Test

# init class
test  = Test()

# allow setter
test.someProperty = 3

# allow getter
if test.someProperty == 3:
  # do something

Thanks for @YannickJadoul for providing the cpp code.