Mixin class data
paul.moore at atosorigin.com
Thu Oct 10 12:06:30 CEST 2002
Greg Ewing <see_reply_address at something.invalid> wrote in message news:<3DA4B561.1040906 at something.invalid>...
> Paul Moore wrote:
> > I'd rather not make it a requirement of
> > this particular mixin that the derived class call its __init__ routine
> Why not? It seems perfectly reasonable to me that
> if you inherit something you should be responsible
> for making sure it's initialised properly.
Mainly because the normal use will be to define a derived class wich
is nothing more than an accumulation of the base and the required
mixins. So the user will normally do:
class MyClass(B, M1, M3):
Having to say (in effect):
"""If you use mixin M2, you need to define an __init__ like
but for all other mixins, you don't need an __init__ of your own"""
seems contrived, at best...
In practice, B is a subclass of StreamRequestHandler which handles
incoming requests and breaks them into command/argument pairs. The
mixins then provide handlers for the standard commands (and callback
to the *server* subclass for implementation, available as self.server,
rather than to the derived handler class). Given that extending TCP
protocols is not normal, the user class ends up being a behaviourless
accumulation of mixins.
Maybe I'm abusing (multiple) inheritance here, by overusing the mixin
concept. But I recall this style well from other languages (notably
OakLisp, an object-oriented Scheme dialect) where it worked extremely
More information about the Python-list