I'm deriving from a base class in a library I use (in other words, I can't change it), and this class declares:

virtual string& getFilename(void) const; virtual void setFilename(const string&);

The base class itself doesn't declare a member to store the file name; it just ignores 'setFilename', and returns an empty string for 'getFilename'. I'd like to implement these routines, but I don't want to have a string reference in my derived class. If possible, I'd like to use a shared_ptr<string>. However, I can't see a simple way to do this. The original string is supplied by me to the library, which eventually calls my 'setFilename'. So, I could start with a shared_ptr, and use operator() to supply the library with a reference to the string. However, when the string& gets back to my 'setFilename', there's no obvious way to get back to the original shared_ptr. Have I missed something? Is there a clean way to implement this with shared_ptr<string>? Thanks.