I would like to return filtering_istream via std::unique_ptr<std::iostream> so that client code can just use iostream interface without knowing what is actual stream type.

Inside the factory function filtering_istream is prepared with possible filters attached. Problem is filters are attached by reference. My question is: how to elegantly attach filters to a filtering_istream so that they live as long as filtering_istream itself? How to attach a filter via shared_ptr for example?

Regards,

Szymon Gatner