From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 10.99.36.130 with SMTP id k124mr34127987pgk.25.1483532320531;
        Wed, 04 Jan 2017 04:18:40 -0800 (PST)
X-Received: by 10.157.37.151 with SMTP id q23mr2686146ota.4.1483532320486;
 Wed, 04 Jan 2017 04:18:40 -0800 (PST)
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!news.glorb.com!b123no172073itb.0!news-out.google.com!u18ni3182ita.0!nntp.google.com!b123no172064itb.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Wed, 4 Jan 2017 04:18:40 -0800 (PST)
In-Reply-To: <o4gcji$4qr$1@gioia.aioe.org>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=194.154.216.88;
 posting-account=sDyr7QoAAAA7hiaifqt-gaKY2K7OZ8RQ
NNTP-Posting-Host: 194.154.216.88
References: <29380aa7-0c3b-4908-94c6-aa91f3996b42@googlegroups.com>
 <o4dn2s$nj6$1@dont-email.me> <o4doud$rg3$1@dont-email.me>
 <bb087830-32e3-4d06-a102-979e9a1e6d68@googlegroups.com>
 <o4g7b3$ba6$2@dont-email.me>
 <b4e8159d-56e0-499b-9a07-35fbf4d43c7e@googlegroups.com>
 <o4gcji$4qr$1@gioia.aioe.org>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <f83b387d-01f4-48c0-8751-e21c7c27a9be@googlegroups.com>
Subject: Re: Experimenting with the OOP features in Ada
From: Laurent <lutgenl@icloud.com>
Injection-Date: Wed, 04 Jan 2017 12:18:40 +0000
Content-Type: text/plain; charset=UTF-8
Xref: news.eternal-september.org comp.lang.ada:33038
Date: 2017-01-04T04:18:40-08:00
List-Id: <comp.lang.ada>

On Tuesday, 3 January 2017 15:31:16 UTC+1, Dmitry A. Kazakov  wrote:
> On 2017-01-03 14:57, Laurent wrote:
> 
> > The only thing which I am not able to see is if I can transform this into a
> > procedure and how I would do it. The Ptr confuses me because I don't
> > understand where it should point to in a procedure.
> > > > > > > >
> >    function Create (Value : String) return My_Safe_String
> >    is
> >       Ptr : My_String_Ptr := new My_String (Value'Length);
> >    begin
> >       Ptr.Value := Value;
> >       return Ref (Ptr);
> >    end Create;
> > > > > > > 
> In the sample code this procedure is called Copy. Regarding using 
> in-place notation that would be:
> 
>     Value.Set (new My_String'(Object.Entity with Value'Length, Value));
> 
> > Item.Name.Set (Name=>"Something") looks better than
> > > > > > > >
> > Item.Name := My_Strings.Handle.Create (Value => Name);
> > > > > > > 
> Some people like using unary "+" for this. E.g.
> 
>     function "+" (Value : String) return My_Safe_String
>        renames My_Strings.Handle.Create;
> 
> Then you can do:
> 
>     Item.Name := +"Something";
> 
> -- 
> Regards,
> Dmitry A. Kazakov
> http://www.dmitry-kazakov.de
> 
> > > 
The solution with the unary "+" sounds familiar. Forgot only that it was
possible.
Looks less complicate than the other solution.

Other thing I don't understand:

For the persistent storage solution I need those handles. So I tried to adapt
the Base_Types package by copying the Safe_Strings example.

with My_Strings;
with My_Strings.Handle;
with Object;

package Base_Types is

   type Object is abstract new Object.Entity with private;
   
   subtype Name_Type is My_Strings.Handle.My_Safe_String;
   subtype Code_SIL_Type is My_Strings.Handle.My_Safe_String;

   procedure Set_Name (Item : in out Object; Name : String) is abstract;
   procedure Set_Code_SIL (Item : in out Object; Code_SIL : String) is abstract;

   function Name_Value (Item : Object) return String is abstract;
   function Code_SIL_Value (Item : Object) return String is abstract;

private

   type Object 
   is abstract new Object.Entity with
      record
         Name     : Name_Type;
         Code_SIL : Code_SIL_Type;
      end record;
   
   type Base_Type_Ptr is access Object'Class;

end Base_Types;

There seems to be no place where I can insert an tagged keyword? Is that
possible or do I have to do it differently?

When I compile this I get a few errors:

and some more of the following but they are just a symptom not the cause:

test.adb:16:23: invalid prefix in selected component "Test_Antibiotic"
test.adb:16:38: prefixed call is only allowed for objects of a tagged type

base_types.ads:7:32: object "Object" cannot be used before end of its
declaration
base_types.ads:22:20: type "Object" cannot be used before end of its declaration
base_types.ads:28:33: tagged type required, found type "Object" defined at line
21

base_types-antibiotics.ads:12:4: subprogram "Name_Value" is not overriding

Thanks