pybind11 通过引用访问私有 class 成员

Question

I am given a class with a private variable locked_ . This variable can be accessed via the methods bool& locked(); and bool locked() const;

class Test {
    
  bool& locked();
  bool locked() const;
    
 private:
  bool locked_{true};
};

I am not allowed to alter class Test , yet I must write a pybind11 interface that allows both setting and retrieving locked_ .

I cannot use .def_readwrite("locked", &Test::locked_); since locked_ is of course private. My attempts using

.def("locked", static_cast<bool& (Test::*)()>(&Test::locked), "locked", py::return_value_policy::reference_internal);

did compile however merely return a bool and not some sort of modifiable reference to bool.

How can I make locked read/write accessible without "touching" the original C++ implementation.

Answer 1

I still don't know pybind but I am starting to learn from your questions and I remember that def accepts lambdas. You can wrap the call to the member like this:

auto locker = [](Test& t, bool lock) { t.locked() = lock; };

I am not sure if you need to do something extra to make def work with your custom Test , so I suppose it can be used like this:

m.def("locker", locker);