Ethan Jucovy wrote:
> On Thu, Dec 17, 2009 at 10:15 AM, Martijn Faassen
> <faas...@startifact.com> wrote:
>> * It'd be nice if __call__ came back with a LookupError instead of
>> a TypeError, but how to get from A to B without breakage?
> Maybe I've misunderstanding, but what's the advantage of making
> IFoo(x) raise a LookupError instead of a TypeError? I've tried to
> follow the thread but I've been confused about this. I do rely on
> catching TypeErrors quite often in my code -- I had thought it was
> intended as part of the API.
Consistency. The other lookup APIs in zope.component raise
ComponentLookupError, which is a kind of LookupError.
Good data point about catching TypeError though - I don't think we can
just make a release that breaks this.
> I like that treating it as typecasting instead of lookup blurs the
> conceptual distinction between "adapting x to IFoo" and "asserting x
> implements IFoo directly" -- when I actually want to know one or the
> other I can use explicit adaptation or check providedBy. In other
> words I use IFoo(x) when I don't care whether IFoo(x) == x.
Yeah, TypeError makes sense from the type casting perspective.
Perhaps my earlier idea about a new Error that subclasses both TypeError
and LookupError isn't so ugly after all.. After all a failure to look up
an adapter can easily be interpreted as both.
Zope-Dev maillist - Zope-Dev@zope.org
** No cross posts or HTML encoding! **
(Related lists -