叶片类型

类型声明：

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

类型正文：

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;