AW: AW: Object Types in PL/SQL

Hi

The default constructor is always there, even if you don't provide one. So, if you declare and implement a constructor that has the same signature as the default constructor (simply all the attributes as IN parameters, returning SELF), you automatically override the default constructor. That is what I want to do. The object type compiles, but if I use it, PL/SQL tells me that it finds more than one constructors with that signature, which are the "hidden" default constructor and the one I implemented (I think). Now, that leaves me clueless, since it should be possible (manual says so) to override the default constructor from 9.2 on.

Any more ideas ?

Stefan Jahnke
Consultant
BOV Aktiengesellschaft
Tel.: +49 201/45 13-289
mailto:stefan.jahnke_at_nospam.bov.de
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-----Ursprüngliche Nachricht-----
Von: rgaffuri_at_cox.net [mailto:rgaffuri_at_cox.net] Gesendet: Dienstag, 15. Juli 2003 14:44
An: Multiple recipients of list ORACLE-L Betreff: Re: AW: Object Types in PL/SQL

ok then i missed it. where is the overriding taking place? I saw a base constructor.. where was the 'override'?
>
> From: Stefan Jahnke <Stefan.Jahnke_at_bov.de>
> Date: 2003/07/15 Tue AM 08:30:30 EDT
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Subject: AW: Object Types in PL/SQL
>
> Hi
>
> The anonnymous block at the bottom of my email is just a little test
driver.
> Basically, I don't use subtyping here. I just override the default
> constructor.
> If I don't implement a constructor at all, I would look like this:
>
> CREATE OR REPLACE TYPE tVNR AS OBJECT
> (
>
> vVNR VARCHAR2(14),
>
> MEMBER FUNCTION getVNR
> RETURN VARCHAR2
>
> ) INSTANTIABLE FINAL;
>
> CREATE OR REPLACE TYPE BODY tVNR AS
>
> MEMBER FUNCTION getVNR RETURN VARCHAR2 IS
> BEGIN
> RETURN SELF.vVNR;
> END;
> END;
>
> And I would get a hidden, system provided default constructor.
> That would allow me to do the following (tested it):
>
> declare
> vVNR tVNR;
> begin
> vVNR := new tVNR('12345678901');
> dbms_output.put_line(vVNR.getVNR());
> end;
>
> And I would get the output:
>
> 12345678901
>
> Unfortunately, that doesn't give me any control regarding the
initialization
> of vVNR.
> Explanation: VNR = "Versichertennummer", which is kind of the Swiss analog
> to the
> US Social Security ID, only less unique ;).
>
> We don't use Object Relational features IN the database. Just plain
> relational tables.
> What we would like to use are Object Types to encapsulate certain things
> like the above
> shown VNR to ensure data integrity during data conversion for PL/SQL
> programs using
> these types. It's more of a guideline where the developers are constrained
> to use the
> types for certain stuff.
>
> Enjoy your day,
>
> Stefan Jahnke
> Consultant
> BOV Aktiengesellschaft
> Tel.: +49 201/45 13-289
> mailto:stefan.jahnke_at_nospam.bov.de
> http://www.bov.de
> Abonnieren Sie unseren Newsletter: http://www.bov.de/enews
>
> Kosten senken - strategische IT-Ziele erreichen! BOV Microsoft Day am
> 24.07.03 in Essen. Anmeldung unter http://www.bov.de/microsoft-day oder
> mailto:andrea.palluck_at_bov.de.
>
> Wie Sie wissen, koennen ueber das Internet versandte E-Mails leicht unter
> fremden Namen erstellt oder manipuliert werden. Aus diesem Grunde bitten
wir
> um Verstaendnis dafuer, dass wir zu Ihrem und unserem Schutz die
rechtliche
> Verbindlichkeit der vorstehenden Erklaerungen und Aeusserungen
> ausschliessen.
>
> As you are probably aware, e-mails sent via the Internet can easily be
> copied or manipulated by third parties. For this reason we would ask for
> your understanding that, for your own protection and ours, we must decline
> all legal responsibility for the validity of the statements and comments
> given above.
>
>
> -----Ursprüngliche Nachricht-----
> Von: rgaffuri_at_cox.net [mailto:rgaffuri_at_cox.net]
> Gesendet: Dienstag, 15. Juli 2003 14:05
> An: Multiple recipients of list ORACLE-L
> Betreff: Re: Object Types in PL/SQL
>
>
> if im reading your code right... looks like your overriding in an
anonymous
> block. in most OO languages overriding is done by a child class. i dont
see
> any subclassing here? didnt they add sub-types and 'extends' to 9.2?
>
> btw, are you using object oriented design in your database? How efficient
do
> you find that?
> >
> > From: Stefan Jahnke <Stefan.Jahnke_at_bov.de>
> > Date: 2003/07/15 Tue AM 06:49:25 EDT
> > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > Subject: Object Types in PL/SQL
> >
> > Hi list
> >
> > I have a problem regardint PL/SQL Object Types. According to the fine
> > manual, it should be
> > possible to override the default constructor (I'm on 9.2.0.3.0 Win2k). I
> did
> > that, Object Type
> > compiles without complaints:
> >
> > CREATE OR REPLACE TYPE tVNR AS OBJECT
> > (
> >
> > vVNR VARCHAR2(14),
> >
> > CONSTRUCTOR FUNCTION tVNR(piVNR VARCHAR2)
> > RETURN SELF AS RESULT,
> >
> > MEMBER FUNCTION getVNR
> > RETURN VARCHAR2
> >
> > ) INSTANTIABLE FINAL;
> >
> > CREATE OR REPLACE TYPE BODY tVNR AS
> >
> > CONSTRUCTOR FUNCTION tVNR(piVNR VARCHAR2)
> > RETURN SELF AS RESULT IS
> > BEGIN
> > IF (LENGTH(piVNR)=11) THEN
> > SELF.vVNR := SUBSTR(piVNR,1,4) || '.' || SUBSTR(piVNR,5,4) || '.'
||
> > SUBSTR(piVNR,9,3);
> > ELSE
> > SELF.vVNR := 'invalid';
> > END IF;
> > RETURN;
> > END;
> >
> > MEMBER FUNCTION getVNR RETURN VARCHAR2 IS
> > BEGIN
> > RETURN SELF.vVNR;
> > END;
> > END;
> >
> > Now, everytime I want to create an object like this:
> >
> > declare
> > vVNR tVNR;
> > begin
> > vVNR := new tVNR('12345678901');
> > dbms_output.put_line(vVNR.getVNR());
> > end;
> >
> > I get the following error message:
> >
> > ERROR at line 4:
> > ORA-06550: line 4, column 15:
> > PLS-00307: too many declarations of 'TVNR' match this call
> > ORA-06550: line 4, column 3:
> > PL/SQL: Statement ignored
> >
> > Looks to me like the PL/SQL enginge isn't able to distinguish the
default
> > constructor from the
> > overridden (my) version, since they have the same signature (of course).
> >
> > Any input ? I couldn't find ANY descenct hints in the fine manual or the
> > Feuerstein book :(.
> >
> > TIA,
> > Stefan
> >
> >
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > --
> > Author: Stefan Jahnke
> > INET: Stefan.Jahnke_at_bov.de
> >
> > Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> > San Diego, California -- Mailing list and web hosting services
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> >
> >
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: <rgaffuri_at_cox.net
> INET: rgaffuri_at_cox.net
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
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>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Stefan Jahnke
> INET: Stefan.Jahnke_at_bov.de
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: <rgaffuri_at_cox.net
  INET: rgaffuri_at_cox.net

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