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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Self pointer in limited record
Newsgroups: comp.lang.ada
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Date: Mon, 10 Sep 2007 21:00:15 +0200
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Date: 2007-09-10T20:59:33+02:00
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On Mon, 10 Sep 2007 16:27:50 -0000, amado.alves@gmail.com wrote:

> FWIW, the problem was the following. I am writing a library. I wanted
> to provide a function to the user to allow him to specify the parent
> of an object in a simple way e.g.
>   Parent_Object : Object := Lookup (Name = "foo foo");
>   Object : Object := Create (Name => "bla bla", Parent =>
> Parent_Object);

What happens when the parent gets finalized before its child? The point is
that if you have a reference semantics, then probably Object must be a
reference. So access Obkect'Class were a better design. If you want to hide
references, then you should use smart pointers instead.
 
> The idea was to have a clean profile like
>    Create (Name : String; Parent : Object);
> instead of
>    Create (Name : String; Parent : access Object);
> 
> Inside the function there is code like
>    New_Object.Parent := Parent.Self; -- (clean profile)
> or
>    New_Object.Parent := Parent; -- ('dirty' profile)
> 
> I am kind of redesigning the library now so these issues are yet in
> flux.

I why don't you use Ada.Finalization.Limited_Controlled? Copying linked
objects is suspicious anyway. When you copy a parent what happens with its
children? Limited_Controlled is always aliased and by-reference.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de