On 7/8/06, Jeremy Day <jeremy.day@gmail.com> wrote:
If you go with references, what would happen in this situation:
<snipped code> It all really boils down to the implementation of get_exception_info(T &) and exception_info. Consider that let's say exception_info is defined this way (for simplicity's sake): [untested] class default_exception; class exception_info : boost::noncopyable { private: bool is_valid; protected: exception_info() : is_valid(true) { }; void set_valid(bool b) { is_valid = b ; }; public: static default_exception _default; operator bool() { return is_valid; }; // ... other operations ... }; class default_exception : public exception_info { public: default_exception () { set_valid(false); } }; template < typename T > exception_info & get_exception_info (T & e) const { exception_info * p = dynamic_cast<exception_info>(&e); return (p == NULL) ? exception_info::_default : *p; }; So when you always get a reference to an object of type exception_info or derivatives, you can specialize the null object case -- and give the client code a consistent handle to the exception. It might count as too much voodoo to get something to return a reference, but the benefits outweight the costs IMO. It just makes the interface less "fool proof" and makes it harder to "shoot yourself in the foot" when using a library of this utility. HTH -- Dean Michael C. Berris C/C++ Software Architect Orange and Bronze Software Labs http://3w-agility.blogspot.com/ http://cplusplus-soup.blogspot.com/ Mobile: +639287291459 Email: dean [at] orangeandbronze [dot] com