Should I expose a protected std::vector?

Question

I have a class which I intend for others to inherit from. It has a std::vector which I only want developers to be able to read from, but not modify, my base functions modify it. Should I provide a function that returns a const iterator, or expose the vector as protected.

Thanks

Answer 1

If you expose the vector as protected, subclasses will be able to modify it. So, you should expose methods that return const iterators.

You can use the Non-Virtual Interface idiom to expose different interfaces for users and subclasses.

Answer 2

If you protected it, then you lose your protection because any subclass can change it to public and let others to modify it.

Why not provide a const reference? If return const iterator, you may need to rewrite a lot interfaces including begin, end, size etc.