[Zope3-dev] Interface declaration API

[Barry A. Warsaw]

>>>>> "JH" == Jeremy Hylton <jeremy@zope.com> writes:

    JH> If you are using inheritance just for implementation purposes
    JH> and you don't want to claim to implement A's interfaces, then
    JH> you should explicitly declare the interface(s) that B
    JH> implements.

If you were using inheritance for implementation purposes and not for
substitutability, wouldn't it make more sense to factor out the common
implementation into a common base class that (explicitly?) made no
interface assertions?  Then you'd share implementation by inheritance
but wouldn't get caught up in messy interface inheritances.

-Barry