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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Question about OO programming in Ada
Date: Tue, 25 Nov 2003 14:17:58 -0600
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Date: 2003-11-25T14:17:58-06:00
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"Ekkehard Morgenstern" <ekkehard.morgenstern@onlinehome.de> wrote in message
news:bq092s$9ph$1@online.de...
> Hi guys,
>
> I have a question about object-oriented programming in Ada:
>
> Do I have to use class-wide types for object-oriented programming, or
could
> I use regular access types?
>
> Like, when I declare a procedure
>
>     procedure A ( B: in access all T'Class )
>
> could I use a different method and still get all the benefits of Ada
> object-oriented programming?

Yikes! The "in" isn't allowed here, nor is the "all" -- they're both
assumed.

Second, you are generally best off avoiding access types when you can. That
certainly is true of O-O programming as well. Use access types for dynamic
structures; don't use them otherwise.

    procedure A (B : in out T'Class);

works just as well and doesn't have explicit access types.

When we designed Claw (a thick O-O interface for Windows), we avoided use of
access types in the interface in almost all cases. There are a lot of access
types in the implementation, but the user of Claw doesn't need to worry
about that. That's especially useful for simple programs (for instance,
those that declare just a few windows), because Ada can do all of the
storage management.

Ada allows access types for O-O programming because of a desire to allow
people to translate existing O-O designs for C++ and Java directly into Ada.
I think that's generally a mistake -- Ada can do better than using explicit
pointers.

                 Randy Brukardt.