objinit.sql

介绍Oracle PL SQL编程

/*
 * ObjInit.sql
 * Chapter 14, Oracle10g PL/SQL Programming
 * by Ron Hardman, Mike McLaughlin, Scott Urman
 *
 * This script demonstrates object initialization.
 */

exec clean_schema.synonyms
exec clean_schema.tables
exec clean_schema.objects


CREATE OR REPLACE TYPE discount_price_obj AS OBJECT (
   discount_rate   NUMBER (10, 4),
   price           NUMBER (10, 2),
   CONSTRUCTOR FUNCTION discount_price_obj (price NUMBER)
      RETURN SELF AS RESULT
)
INSTANTIABLE FINAL;
/

CREATE OR REPLACE TYPE BODY discount_price_obj
AS
   CONSTRUCTOR FUNCTION discount_price_obj (price NUMBER)
      RETURN SELF AS RESULT
   AS
   BEGIN
      SELF.price := price * .9;
      RETURN;
   END discount_price_obj;
END;
/

prompt
prompt Doesn't work - results in the following message:
prompt  ORA-06530: Reference to uninitialized composite
prompt

DECLARE
   v_price   discount_price_obj;
BEGIN
   v_price.price := 75;
   DBMS_OUTPUT.put_line (v_price.price);
END;
/

prompt
prompt This example works
prompt

DECLARE
   v_price   discount_price_obj := discount_price_obj (NULL, NULL);
BEGIN
   v_price.price := 75;
   DBMS_OUTPUT.put_line (v_price.price);
END;
/