Re: Inherited Methods and such

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
news:7p6gc1s9imfa$.kmvwf5zyf8e9.dlg@40tude.net...
...
>> This doesn't begin to make sense. The object hasn't even found out what
it's
>> border it (because it hasn't been constructed), and you want to ask what
it
>> is?

>Surely. The base type does not know what border it has. It only knows that
>there is one and it wants to ask for. This is nothing special, it is an
>abstract primitive operation.

But there is no reason for the base window to do anything with the border,
because it knows nothing about the implementation. That information surely
can have nothing to do with the construction of the base window (otherwise
you have a serious data coupling problem), so there is no reason for the
window to ask about it during construction.

> > Dispatching in a constructor is a bug, period.
>
> No, that depends on what is constructor and what is being constructed.
>
> The point is that it is perfectly reasonable and consistent to dispatch at
> the end of construction of T'Class, It is wrong to dispatch before that.

It makes sense to dispatch *after* the end of the construction, not at any
point during it. Any operation for which this makes sense cannot have
anything to do with construction. Mixing such operations up with
constructors is just confusing, and certainly bad design.

> Further, Ada.Finalization.Initialize already *dispatches* right from
there.
> It seemingly made sense for the designers of Ada 95. Why Get_Border_Type
> does not?

Because it was a hack to provide a hook. Just because it is in the language
doesn't make it good design! The whole of Ada.Finalization.Controlled is a
hack - the dispatching is just a cover for a lack of will to include the
proper magic for hooks. And because it is a hack, you can starting asking
questions that are inappropriate. I think it is best to ignore Initialize as
much as possible, and for Ada 2007, use constructor functions instead.

                                    Randy.