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From: "David Botton" <dbotton@hotmail.com>
Subject: Exposing agreggate members of a class
Date: 1998/12/30
Message-ID: <76cd39$21c8$1@news.gate.net>#1/1
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Organization: CyberGate, Inc.
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Newsgroups: comp.lang.ada
Date: 1998-12-30T00:00:00+00:00
List-Id: <comp.lang.ada>

Given:

with GCanvas_Package; use GCanvas_Package;

type GWindow_Object is tagged with private;
type GWindow_Pointer is access all GWindow_Object;

private:

type GWindow_Object is tagged
   record
        Canvas : GCanvas_Object;
   end record;

What is the cleanest way to give access to the Canvas by reference in a way
that will not require Unchecked Programming

What I don't want:

    function Get_Canvas( window : in GWindow_Object ) return GCanvas_Pointer
is
    begin
        return window.Canvas'Unchecked_Access;
    end Get_Canvas;

Which on top of the Unchecked_Access issue means that consumers of such a
class would have to dereference first to use the GCanvas_Object methods:

declare
    Canvas : GCanvas_Pointer := Get_Canvas( window );
begin
    Draw_Line(Canvas.all, 10, 10, 100, 100);
end;

Of course you could write the methods to accept GCanvas_Pointer's, but I
want to avoid the use of Access variables when possible.

Thanks,
David Botton