plsql
Objekttypen

Bemerkungen

l_obj := BASE_TYPE(1, 'Default', 1);

BASISTYP

Typdeklaration:

CREATE OR REPLACE TYPE base_type AS OBJECT
(
   base_id     INTEGER,
   base_attr   VARCHAR2(400),
   null_attr   INTEGER, -- Present only to demonstrate non-default constructors
   CONSTRUCTOR FUNCTION base_type
   (
      i_base_id INTEGER,
      i_base_attr VARCHAR2
   ) RETURN SELF AS RESULT,
   MEMBER FUNCTION get_base_id RETURN INTEGER,
   MEMBER FUNCTION get_base_attr RETURN VARCHAR2,
   MEMBER PROCEDURE set_base_id(i_base_id INTEGER),
   MEMBER PROCEDURE set_base_attr(i_base_attr VARCHAR2),
   MEMBER FUNCTION to_string RETURN VARCHAR2
) INSTANTIABLE NOT FINAL

Typ Körper:

CREATE OR REPLACE TYPE BODY base_type AS
   CONSTRUCTOR FUNCTION base_type
   (
      i_base_id INTEGER,
      i_base_attr VARCHAR2
   ) RETURN SELF AS RESULT
   IS
   BEGIN
      self.base_id := i_base_id;
      self.base_attr := i_base_attr;
      RETURN;
   END base_type;

   MEMBER FUNCTION get_base_id RETURN INTEGER IS
   BEGIN
      RETURN self.base_id;
   END get_base_id;

   MEMBER FUNCTION get_base_attr RETURN VARCHAR2 IS
   BEGIN
      RETURN self.base_attr;
   END get_base_attr;

   MEMBER PROCEDURE set_base_id(i_base_id INTEGER) IS
   BEGIN
      self.base_id := i_base_id;
   END set_base_id;

   MEMBER PROCEDURE set_base_attr(i_base_attr VARCHAR2) IS
   BEGIN
      self.base_attr := i_base_attr;
   END set_base_attr;

   MEMBER FUNCTION to_string RETURN VARCHAR2 IS
   BEGIN
      RETURN 'BASE_ID ['||self.base_id||']; BASE_ATTR ['||self.base_attr||']';
   END to_string;
END;

MID_TYPE

Typdeklaration:

CREATE OR REPLACE TYPE mid_type UNDER base_type
(
   mid_attr DATE,
   CONSTRUCTOR FUNCTION mid_type
   (
      i_base_id   INTEGER,
      i_base_attr VARCHAR2,
      i_mid_attr  DATE
   ) RETURN SELF AS RESULT,
   MEMBER FUNCTION get_mid_attr RETURN DATE,
   MEMBER PROCEDURE set_mid_attr(i_mid_attr DATE),
   OVERRIDING MEMBER FUNCTION to_string RETURN VARCHAR2
) INSTANTIABLE NOT FINAL

Typ Körper:

CREATE OR REPLACE TYPE BODY mid_type AS
   CONSTRUCTOR FUNCTION mid_type
   (
      i_base_id   INTEGER,
      i_base_attr VARCHAR2,
      i_mid_attr  DATE
   ) RETURN SELF AS RESULT
   IS
   BEGIN
      self.base_id := i_base_id;
      self.base_attr := i_base_attr;
      self.mid_attr := i_mid_attr;
      RETURN;
   END mid_type;

   MEMBER FUNCTION get_mid_attr RETURN DATE IS
   BEGIN
      RETURN self.mid_attr;
   END get_mid_attr;

   MEMBER PROCEDURE set_mid_attr(i_mid_attr DATE) IS
   BEGIN
      self.mid_attr := i_mid_attr;
   END set_mid_attr;

   OVERRIDING MEMBER FUNCTION to_string RETURN VARCHAR2
   IS
   BEGIN
      RETURN (SELF AS base_type).to_string || '; MID_ATTR [' || self.mid_attr || ']';
   END to_string;
END;

LEAF_TYPE

Typdeklaration:

CREATE OR REPLACE TYPE leaf_type UNDER mid_type
(
   leaf_attr VARCHAR2(1000),
   CONSTRUCTOR FUNCTION leaf_type
   (
      i_base_id   INTEGER,
      i_base_attr VARCHAR2,
      i_mid_attr  DATE,
      i_leaf_attr VARCHAR2
   ) RETURN SELF AS RESULT,
   MEMBER FUNCTION get_leaf_attr RETURN VARCHAR2,
   MEMBER PROCEDURE set_leaf_attr(i_leaf_attr VARCHAR2),
   OVERRIDING MEMBER FUNCTION to_string RETURN VARCHAR2
) INSTANTIABLE FINAL

Typ Körper:

CREATE OR REPLACE TYPE BODY leaf_type AS
   CONSTRUCTOR FUNCTION leaf_type
   (
      i_base_id   INTEGER,
      i_base_attr VARCHAR2,
      i_mid_attr  DATE,
      i_leaf_attr VARCHAR2
   ) RETURN SELF AS RESULT
   IS
   BEGIN
      self.base_id := i_base_id;
      self.base_attr := i_base_attr;
      self.mid_attr := i_mid_attr;
      self.leaf_attr := i_leaf_attr;
      RETURN;
   END leaf_type;

   MEMBER FUNCTION get_leaf_attr RETURN VARCHAR2 IS
   BEGIN
      RETURN self.leaf_attr;
   END get_leaf_attr;

   MEMBER PROCEDURE set_leaf_attr(i_leaf_attr VARCHAR2) IS
   BEGIN
      self.leaf_attr := i_leaf_attr;
   END set_leaf_attr;

   OVERRIDING MEMBER FUNCTION to_string RETURN VARCHAR2 IS
   BEGIN
      RETURN (SELF AS mid_type).to_string || '; LEAF_ATTR [' || self.leaf_attr || ']';
   END to_string;
END;

Zugriff auf gespeicherte Objekte

CREATE SEQUENCE test_seq START WITH 1001;

CREATE TABLE test_tab
(
   test_id  INTEGER,
   test_obj base_type,
   PRIMARY KEY (test_id)
);

INSERT INTO test_tab (test_id, test_obj)
VALUES (test_seq.nextval, base_type(1,'BASE_TYPE'));
INSERT INTO test_tab (test_id, test_obj)
VALUES (test_seq.nextval, base_type(2,'BASE_TYPE'));
INSERT INTO test_tab (test_id, test_obj)
VALUES (test_seq.nextval, mid_type(3, 'MID_TYPE',SYSDATE - 1));
INSERT INTO test_tab (test_id, test_obj)
VALUES (test_seq.nextval, mid_type(4, 'MID_TYPE',SYSDATE + 1));
INSERT INTO test_tab (test_id, test_obj)
VALUES (test_seq.nextval, leaf_type(5, 'LEAF_TYPE',SYSDATE - 20,'Maple'));
INSERT INTO test_tab (test_id, test_obj)
VALUES (test_seq.nextval, leaf_type(6, 'LEAF_TYPE',SYSDATE + 20,'Oak'));

Gibt eine Objektreferenz zurück:

SELECT test_id
      ,test_obj
  FROM test_tab;

Gibt die Objektreferenz zurück und drückt alle auf den Untertyp

SELECT test_id
      ,TREAT(test_obj AS mid_type) AS obj
  FROM test_tab;

Gibt einen String-Deskriptor für jedes Objekt nach Typ zurück

SELECT test_id
      ,TREAT(test_obj AS base_type).to_string() AS to_string -- Parenthesis are needed after the function name, or Oracle will look for an attribute of this name.
  FROM test_tab;