On Apr 14, 2011, at 3:32 PM, Ricardo Kirkner wrote:
What would the semantics be of a super that intentially calls all siblings? In particular what is the return value of such a call? The implementation can't know how to combine the implementations in the inheritance chain and should refuse the tempation to guess.
I'll give you the example I came upon:
I have a TestCase class, which inherits from both Django's TestCase and from some custom TestCases that act as mixin classes. So I have something like
class MyTestCase(TestCase, Mixin1, Mixin2): ...
now django's TestCase class inherits from unittest2.TestCase, which we found was not calling super. Even if this is a bug and should be fixed in unittest2, this is an example where I, as a consumer of django, shouldn't have to be worried about how django's TestCase class is implemented. Since I explicitely base off 3 classes, I expected all 3 classes to be initialized, and I expect the setUp method to be called on all of them.
If I'm assuming/expecting unreasonable things, please enlighten me.
For cooperative-multiple-inheritance to work, the classes need to cooperate by having been designed to work together in a series of cooperative super calls. If an external non-cooperative class needs to be used, then it should be wrapped in a class that makes an explicit __init__ call to the external class and then calls super().__init__() to continue the forwarding. Raymond