SQL & PL/SQL

Hi to all!

I created an object using:

CREATE OR REPLACE TYPE some_object AS OBJECT
(
some_information NUMBER,
MEMBER FUNCTION some_function RETURN NUMBER
)

and when I tried to implement member function "some_function" that need to change value of variable "some_information" like:

CREATE OR REPLACE TYPE BODY some_object AS

MEMBER FUNCTION some_function RETURN NUMBER IS
BEGIN
some_information := some_information + 5;
RETURN some_information;
END;

END;

It gives me following error:


Compilation errors for TYPE BODY CMS.SOME_OBJECT

Error: PLS-00363: expression 'SELF.SOME_INFORMATION' cannot be used as an assignment target
Line: 5
Text: some_information := some_information + 5;

The question is:

How to implement my function that can change value of "some_information" ?