Object type with constructor gets PLS-00307 (10g)

Question

Hi all,
I have the following code, and I am getting the following error. I want to have a constructor that can be called without specifying the parameters by name. Is that not possible?
What am I doing wrong?
Thanks!
Error:Error at line 50
ORA-06550: line 5, column 17:
PLS-00307: too many declarations of 'TRANSFEROBJECT_O' match this call
ORA-06550: line 5, column 5:
PL/SQL: Statement ignoredCode:DROP TYPE TransferObject_o
CREATE TYPE
    TransferObject_o
AS OBJECT
    m_objectId  NUMBER(15)
  , m_attribute VARCHAR2(4000)
  , CONSTRUCTOR FUNCTION TransferObject_o
        p_objectId  NUMBER--   := NULL
      , p_attribute VARCHAR2-- := NULL
    ) RETURN SELF AS RESULT
CREATE TYPE BODY
    TransferObject_o
AS
    CONSTRUCTOR FUNCTION TransferObject_o
        p_objectId  NUMBER--   := NULL
      , p_attribute VARCHAR2-- := NULL
    ) RETURN SELF AS RESULT
    IS
    BEGIN
        SELF.m_objectId  := p_objectId;
        SELF.m_attribute := p_attribute;
        RETURN;
    END;
END;
DECLARE
    l_object TransferObject_o;
BEGIN
    l_object := TransferObject_o(1, 'B');
END;
/

Answer 1

Hi,
When you create an OBJECT, Oracle automatically creates a constructor with one argument for each of the object's attributes. You've created a second constructor, that has the same signature, except that the arguments in your functin are optional. When you call an overloaded routine ( whether it's a constructor or any other function or procedure), Oracle has to decide which of the versions you're calling. If you call the TransferObject_o constructor with fewer than two arguments, the system knows you mean the version you wrote, since the default constructor has two required arguments. But when you call the TransferObject_o constructor with exactly two arguments, it has no way of telling which version to use, and raises an error.
The Oracle 10.1 "PL/SQL User's Guide and Reference" says:
"You can define your own constructor methods, either overriding a system-defined constructor, or defining a new function with a different signature."
I couldn't find an example of overriding the constructor (not that I spent a lot of time looking. If you find one, or figure out how to do it, please post an example or a link here.).
Failing that, you can always give your constructor a different signature (e.g., put the VARCHAR2 argument first).