[SamReidHughes]

> The proposed API in SetStringer seems very dangerous; you're passing back a const ref to a string that isn't really const at all (successive calls after the set has been updated will mutate it's state, users may be unaware of this).

An accessor returning a const reference is perfectly normal. Something being const in C++ never meant that other things can't modify it, and the risk you describe has nothing to do with it being a const reference, as opposed to the non-const kind. For example, one given by the article, in fact, you get the same situation with an even bigger risk profile with the expression v[i], where v is a std::vector<std::string>.

> ref when you want shared ownership.

Not at all. If you have a reference to something, you don't own it.