Reference gives a different guarantee than pointers. Ok Could still be cast to a pointer but ....
T& x = my_obj(); // reference *feels* like more obvious semantics than pointer. x.do_it();
*Ideally* my_obj always holds something... never empty. That is I guess problematic from the implementation viewpoint, as it may cause a large number of allocations. However it makes the thing extremely simple to use. Dont really want to have to do this all the time:
if( !my_obj.is_empty()){ my_obj().do_it(); }
Actually, reference isn't all that different from a pointer except that you can use the dot operator (and operator <<, +, -, ==, etc.) on it without dereferencing first. I think you're looking for "smart references," but C++ doesn't really do them because you can't overload the dot operator. I bet you could get something very close to what you want by defining another class smart_object<T> that inherits from shared_ptr<T>, but suppresses the -> and = operators and has an implicit conversion to T&. (Implicit conversions are often a bad idea, and I don't know if this is an exception, but...) As far as reference semantics, all you really want is a guarantee that a shared_ptr<T> is always initialized to a non-null value, so make sure there is no default constructor and you're in business. I don't know if I recommend actually *doing* this, though. shared_ptr should probably be sufficient for giving you reference semantics, and while it's nice to use operators without dereferencing (*myPtr), it's probably not worth messing with implicit conversions to achieve it. Max
OTOH maybe could do: share_object<T> my_empty_obj(leave_empty()); // then make sure its not empty before going public...
I believe that shared_ptr throws an exception if you try to dereference it while it's empty. If you are mathematically positive that a shared_ptr has a value (e.g. no default constructor), you don't even need to set a catch block (although you still ought to run unit tests, etc.). -- Ubi solitudinem faciunt, pacem appellant. They make a desert and call it peace. -Tacitus