Question

title might be confusing, but lets say I have a template:

template <typename T, size_t offset>
struct offsetedIdxArray
{
//...
}

And after I create an instance:

static const size_t offset(1701);
offsetedIdxArray<zmq::socket_t, offset> oia;

Is there a way to get offset variable from oia. I know I can just use offset but from code style perspective i prefer to get it from oia if possible.

EDIT: I’m looking for a way to get offset without helper variable inside struct…

Answer 1

If you want to obtain the information from an offsetedIdxArray<T,N> object without adding any members to the class template, you can use a template function:

#include <iostream>
#include <cstddef>

template <typename T, size_t offset>
struct offsetedIdxArray
{
};

template <typename T, size_t offset>
size_t getOffset(const offsetedIdxArray<T, offset>&) {
  return offset;
}

int main()
{
   offsetedIdxArray<int,5> oia;
   std::cout << getOffset(oia) << "\n";

}

Otherwise you can add a static constant or enum data member, as suggested in other posts.