Re: Confused about class-wide types

[Mart van de Wege <mvdwege@gmail.com>]

Simon Wright <simon@pushface.org> writes:

> I think this is difficult because you've introduced operations for the
> child (Message_Event) of which the parent (Event) has no analogue at
> all. What is the common operation that all Events must support?
> Maybe something like
>
>    procedure Handle (E : Event) is abstract;
>
> Your procedure Message is a factory, I think; it might be better as
>
>    function Message (Mess : in String) return Message_Event;
>

I was over-designing a bit. At current I only need two classes: an event
with a unstructured String as a Message, and a child event with a bit
more metadata in the record, so I thought I'd start out with an abstract
Event class in my Vector definition, and build the generic operations
first.

Shark8 pointed out the right solution: use an Indefinite_Vector, but
your and Dimitri's posts help a lot with understanding where I went
wrong, thanks.

Mart

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