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

You absolutely should throw an exception from a constructor if you're unable to create a valid object. This allows you to provide proper invariants in your class.

In practice, you may have to be very careful. Remember that in C++, the destructor will not be called, so if you throw after allocating your resources, you need to take great care to handle that properly!

This page has a thorough discussion of the situation in C++.