How to call an Oracle PL/SQL object super method - oracle

Question

I'd like to call an overridden PL/SQL method. Here's an example:
-- super class
create or replace type test as object
(
n number,
member procedure proc(SELF in out nocopy test, s varchar2)
)
alter type test not final
/
create or replace type body test is
member procedure proc(SELF in out nocopy test, s varchar2) is
begin
dbms_output.put_line('test1: n='||nvl(self.n, 'null')||' s='||s);
self.n := to_number(s);
end;
end;
/
-- derived class
create or replace type test2 under test
(
overriding member procedure proc(SELF in out nocopy test2, s varchar2)
)
/
Now I want to invoke the inherited version of the proc method. When I try to do an explicit cast like treat(self as test).proc(s); it won't compile because of PLS-00363: expression 'SYS_TREAT' cannot be used as an assignment target
The type body compiles when I use a local variable:
create or replace type body test2 is
overriding member procedure proc(SELF in out nocopy test2, s varchar2) is
O test;
begin
O := treat(self as test);
O.proc(s);
end;
end;
/
But when I run my example like this
declare
obj test2;
begin
obj := test2(0);
obj.proc('1');
end;
...it throws ORA-21780: Maximum number of object durations exceeded.
Is there any way to call test::proc (without serializing/deserializing)?
And... after proc has been called, how can any changed attributes (namely n) be reflected in obj ?
Update (Thanks, tbone):
I changed the organization of my methods using template methods ('before' and 'after'). I add them whenever I need to extend a method.
create or replace type test as object
(
n number,
member procedure proc (SELF in out nocopy test, s varchar2),
member procedure afterProc (SELF in out nocopy test, s varchar2)
member procedure beforeProc(SELF in out nocopy test, s varchar2),
)
not final
/
create or replace type body test is
member procedure proc(SELF in out nocopy test, s varchar2) is
begin
beforeProc(s);
dbms_output.put_line('test1: n='||nvl(n, 'null')||' s='||s);
n := to_number(s);
afterProc(s);
end;
member procedure afterProc (SELF in out nocopy test, s varchar2) is begin null; end;
member procedure beforeProc(SELF in out nocopy test, s varchar2) is begin null; end;
end;
/

Answer 1

To access the super methods, try either general invocation or generalized expression. For example, using a person supertype and student subtype:
CREATE OR REPLACE TYPE person_typ AS OBJECT (
idno number,
name varchar2(30),
phone varchar2(20),
MAP MEMBER FUNCTION get_idno RETURN NUMBER,
MEMBER FUNCTION show RETURN VARCHAR2)
NOT FINAL;
CREATE OR REPLACE TYPE BODY person_typ AS
MAP MEMBER FUNCTION get_idno RETURN NUMBER IS
BEGIN
RETURN idno;
END;
MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
-- function that can be overriden by subtypes MEMBER FUNCTION show RETURN VARCHAR2 IS BEGIN
RETURN 'Id: ' || TO_CHAR(idno) || ', Name: ' || name;
END;
END;
CREATE TYPE student_typ UNDER person_typ (
dept_id NUMBER,
major VARCHAR2(30),
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2)
NOT FINAL;
CREATE TYPE BODY student_typ AS
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
RETURN (self AS person_typ).show || ' -- Major: ' || major ;
END;
END;
-- Using Generalized Invocation
DECLARE
myvar student_typ := student_typ(100, 'Sam', '6505556666', 100, 'Math');
name VARCHAR2(100);
BEGIN
name := (myvar AS person_typ).show; --Generalized invocation
END;
-- Using Generalized Expression
DECLARE
myvar2 student_typ := student_typ(101, 'Sam', '6505556666', 100, 'Math');
name2 VARCHAR2(100);
BEGIN
name2 := person_typ.show((myvar2 AS person_typ)); -- Generalized expression
END;
EDIT:
If you are on 10g, you'll need to organize the functions a bit different, but same functionality from the child to call the super method:
CREATE TYPE BODY person_typ AS
MAP MEMBER FUNCTION get_idno RETURN NUMBER IS
BEGIN
RETURN idno;
END;
-- static function that can be called by subtypes
STATIC FUNCTION show_super (person_obj in person_typ) RETURN VARCHAR2 IS
BEGIN
RETURN 'Id: ' || TO_CHAR(person_obj.idno) || ', Name: ' || person_obj.name;
END;
-- function that can be overriden by subtypes
MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
RETURN person_typ.show_super ( SELF );
END;
END;
CREATE TYPE student_typ UNDER person_typ (
dept_id NUMBER,
major VARCHAR2(30),
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2)
NOT FINAL;
CREATE TYPE BODY student_typ AS
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
RETURN person_typ.show_super ( SELF ) || ' -- Major: ' || major ;
END;
END;
Now you'd call show_super() from student for the person method, or just show() for the student method.
From the docs, hope that helps.