----- Original Message ----- From: "Daniel James" <daniel@calamity.org.uk> To: <boost@lists.boost.org> Sent: Friday, February 25, 2005 11:16 AM Subject: [boost] Re: Querying usefulness of a macro for inheriting from STLcontainers
christopher diggins wrote: I think publicly inheriting from a class that isn't designed for inheritance is a bad idea. There are type safety problems, non-virtual destructors, slicing etc.
Hi Daniel thanks for the help and suggestions ( and Kevin and Jonathan as well), I have heard here and there, inheriting from STL container is a "bad idea", but I don't specifically know all the reasons why. I am not an expert in this area (heck or any part of C++ for that matter). Isn't it only bad if someone tries to delete the object using a base class pointer? Could we not prevent that idiom by writing type-casts which force failure upon a pointer cast to the inherited type? For instance: public MyCustomContainer : container { operator container*() { throw exception("can not cast to container*"); } ... } Doesn't this solve the virtual destructor problem? Another approach perhaps would be to create inheritable versions of the STL containers which are thin wrappers which simply provide a virtual destructor. Would this not work as well? However what are the other problems of type-safety, slicing(?), etc. to which you allude? I am unfamiliar with them and I am not sure how to go about researching the topic. There is another option of course, which is to use the BIL for delegation. This however has a small overhead which may not be acceptable in some cases. Christopher Diggins Object Oriented Template Library (OOTL) http://www.ootl.org