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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Please - has anyone got a mixed Ada/C++ sample project they could
 share?
Date: Fri, 24 Feb 2017 22:33:16 +0000
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john@mccabe.org.uk writes:

> I'd be particularly interested in one where (if you consider this
> diagram - http://java.dzone.com/sites/all/files/observer_pattern.PNG)
> the Subject and Observer interfaces are defined as C++ abstract base
> classes (i.e. provide only pure virtual functions and no members), the
> ConcreteSubject is [probably] in C++, and ConcreteObserver in Ada with
> an Ada main procedure.

As I understand it, ConcreteSubject.notify() will end up calling
ConcreteObserver.update() for registered observers, which will then know
to get subjectState from the ConcreteSubject. Perhaps subjectState needs
to be publicly visible for this to work? or there are unstated public
operations?

Is Subject abstract? I'd expect there to be some implementation of those
operations somewhere, in Subject would be natural.