kj <[email protected]> wrote:
>
>Suppose that I want to write a subclass C of base classes A and B.
>What considerations should go into choosing the ordering of A and
>B in C's base class list?
>...
>...it is difficult for me to see a strong compelling reason for picking
>an ordering over another. But may be just ignorance on my part.
>
>How should one go about deciding the ordering of base classes?
In general, it is uncommon to have a class that derives from multiple
classes that all provide major functionality. That quickly gets confusing,
which is one reason Java doesn't allow multiple inheritance.
Now, it is very common for a class to derive from one class primarily, with
other classes providing a few additional features. That's the "mix-in"
concept. In that case, you'd list the "major" ancestor first, with the
mix-ins after, so the mix-ins can modify the behavior.
class BlueSpanishListBox( ListBox, ColorBlueMixIn, SpanishMixIn ):
...
Reading it, a BlueSpanishListBox is-a ListBox that happens to have a few
additional features.
--
Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.
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