Enable std::get support on class

Question

What are the templates that I have to specialize to support std::get?

struct MyClass {
  int a;
};

template 
struct MyContainer {
  MyClas         


        

Answer 1

std::get is not a customization point for the standard library; the three function template overloads (for pair, tuple and array) do not explicitly allow for user-defined overloads, so 17.6.4.2.1p1 applies and adding a declaration of your own function template overload is undefined behaviour.

Note that get as an unqualified name is a customization point as of C++17; it is used by the structured binding declaration protocol to access tuple-like elements; but this is as an unqualified name, not the qualified name std::get.

That said, if you were to write:

namespace std {
   template MyClass &get(MyContainer &c) { return c.array[I]; }
}

and similarly for the rvalue reference and const reference overloads, your program would likely work as you expect.

However, there's little point seeing as the standard already supplies array:

template using MyContainer = std::array;