CODEWITHSUNDEEP
pythonc++pybind11
Flo Ryan
Flo Ryan

Reputation: 443

pybind11 access private class member via reference

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.

Upvotes: 1

Views: 1400

Answers (1)

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122830

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);

Upvotes: 2

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