How to compare python objects which wrap pointers to existing C++ structures?
I have a class method that returns a pointer to an inner data structure (where the data structure is guaranteed to outlive its use in python code). It looks like:
class MyClass {
...
some_structure* get() {
return inner_structure_;
}
private:
some_structure* inner_structure_;
};
I want to wrap this get()
method in Boost::Python so that if two different objects of this class return the same pointer, the associated some_structure
objects in python compare equal.
Inside the class_<MyClass>
definition I've tried wrapping get()
with both return_value_policy<reference_existing_object>()
and return_inner_reference<>()
call policies, but in both cases, calling get()
on different python "MyClass" objects returns different some_structure
objects even though all point to the same memory address in C++.
How would I get around this? Might there be a hidden property inside the wrapper object that stores the pointer's a开发者_如何学编程ddress, so I can compare those instead?
Figured out a way to do it, although it still feels hackish and that there should be some easier way. But here goes:
1) Define your own methods that compare the pointers.
template <typename T>
bool eq(const T* self, const T* rhs) {
return self == rhs;
}
template <typename T>
bool ne(const T* self, const T* rhs) {
return !eq<T>(self, rhs);
}
2) Manually declare the __eq__
and __ne__
inside the wrapper class to point to those methods:
class_<smth>("smth", no_init)
...
.def("__eq__", &eq<smth>)
.def("__ne__", &ne<smth>);
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