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

It's always pretty dodgy, especially if you're allocating resources inside a constructor; depending on your language the destructor won't get called, so you need to manually cleanup. It depends on how when an object's lifetime begins in your language.

The only time I've really done it is when there's been a security problem somewhere that means the object should not, rather than cannot, be created.