PLSQL Convert Object to String

Problem & Goal

Usually, like in java, any object will implement its to_string() function. So in Plsql, there is the same requirement.
 We want to implement to_string() in plsql.

Thinking

When one Object' type is basic type in plsql, then the function will return its value. Otherwise, the function will return its typename.

Solution  & Example

CREATE OR REPLACE FUNCTION to_string(obj IN ANYDATA) RETURN VARCHAR2 IS
code PLS_INTEGER;
v_type AnyType;
BEGIN
    code :=obj.getType(v_type);
    CASE 
        code WHEN DBMS_TYPES.TYPECODE_VARCHAR2 THEN
                RETURN  TO_CHAR(obj.AccessVarchar2());
            WHEN DBMS_TYPES.TYPECODE_BDOUBLE THEN
                RETURN TO_CHAR(obj.AccessBDouble());
            WHEN DBMS_TYPES.TYPECODE_BFLOAT THEN
                RETURN TO_CHAR(obj.AccessBFloat());
            WHEN DBMS_TYPES.TYPECODE_NUMBER THEN
                RETURN TO_CHAR(obj.AccessNumber());
        ELSE RETURN obj.getTypeName(); END CASE;
END;
/
show errors;
CREATE OR REPLACE TYPE TEST FORCE AS OBJECT
(id Number,
 name VARCHAR2(20),
 CONSTRUCTOR FUNCTION TEST RETURN SELF AS RESULT);
/
show errors;
CREATE OR REPLACE TYPE BODY TEST AS
 CONSTRUCTOR FUNCTION TEST RETURN SELF AS RESULT IS 
 BEGIN RETURN;END;
END; 
/
show errors;
SET SERVEROUTPUT ON;
DECLARE 
a Number;
b VARCHAR2(20);
c TEST;
BEGIN
    a :=1;
    b:='julia zhang';
    c :=TEST();
    dbms_output.put_line('a:to_string()::::'||to_string(AnyData.convertNumber(a)));
    dbms_output.put_line('b:to_string()::::'||to_string(AnyData.convertVarchar2(b)));
    dbms_output.put_line('c:to_string()::::'||to_string(AnyData.convertObject(c)));
END;
/

Extend

CREATE OR REPLACE FUNCTION AnydataArray1ToString (id IN AnydataArray , for_flatten BOOLEAN ) RETURN
VARCHAR2 IS
i INTEGER ; result_str VARCHAR2 (32767); BEGIN
    result_str  := '';
    FOR i IN 1..id.count
    LOOP
        IF  for_flatten  THEN
            result_str  := result_str  || ', ' || objectToString (id (i ));
        ELSE result_str  := result_str  || objectToString (id (i )); END IF;
    END LOOP;
    IF  for_flatten  THEN RETURN substr (result_str , 3); ELSE
        RETURN result_str ; END IF;
END ;
/

Refference

http://docs.oracle.com/cd/B19306_01/appdev.102/b14258/t_anydat.htm#BEHEICHI