When is it right for a constructor to throw an exception?

Question

When is it right for a constructor to throw an exception? (Or in the case of Objective C: when is it right for an init\'er to return nil?)

It seems to me that a cons

Answer 1

Because of all the trouble that a partially created class can cause, I'd say never.

If you need to validate something during construction, make the constructor private and define a public static factory method. The method can throw if something is invalid. But if everything checks out, it calls the constructor, which is guaranteed not to throw.