Question

i am studying object orienting concepts in oracle and have some confusion in some terms
for example,i know how to create object type,but dont know what does mean not instantiable?

create or replace type compar_item_t as object(
com varchar2(50),
chint varchar2(254),

 not instantiable member function getChint
                  return varchar2,
                 member function print
                  return varchar2
) not instantiable not final;                 

does not instantiable means that we can’t instantiable it?or what does last term means?i meant not instantiable not final; ?

Answer 1

I think this document might be helpful, if you’re not already familiar with it:

http://docs.oracle.com/cd/B19306_01/server.102/b14220/objects.htm

Oracle object technology is a layer of abstraction built on Oracle’s
relational technology.

Which implies “it’s our product, so we’re making up our own terminology as we go along” 😉

Anyway, what does Oracle mean by “instantiable” (a word I’m not sure you’ll find in most dictionaries, and will probably be rejected by most spell-checkers ;))? From the same link:

Declaring a method as NOT INSTANTIABLE means that the type is not
providing an implementation for that method….

A subtype of a NOT INSTANTIABLE type can override any of the
non-instantiable methods of the supertype and provide concrete
implementations. If there are any non-instantiable methods remaining,
the subtype must also necessarily be declared NOT INSTANTIABLE….

So I guess “non-instantiable” is similar to an “abstract base type” or an “interface” in most other OOP languages.

IMHO…