RE: Objects and such

Joe,

Good example.

Might be improved by considering the "pseudo" DLTOBJ command, DEL (aka RMVLNK).

Lastly, and hopefully not to confuse the issue. But Dr. Soltis points out the OS/400 is Object-Based
not Object-Oriented. The difference is Object-Based doesn't use inheritance (and thus doesn't use
polymorphism).

But that doesn't mean polymorphic behavior from the user perspective can't be simulated. As we see in
OS/400 or even our own RPG programs.

If OS/400 was Object-Oriented, we could define our own object types and the DEL command would work
just fine on them.

Charles

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Joe Pluta
Sent: Friday, October 19, 2007 10:21 AM
To: 'RPG programming on the AS400 / iSeries'
Subject: Objects and such

I think, though, that sometimes we get blinded by
terminology. The idea of polymorphism is really pretty
simple, and we do it all the time, especially on the System i:

DLTF, DLTCMD, DLTPGM

If you think of these in object terms, they're really:

F.DLT, CMD.DLT, PGM.DLT

That is, you're sending the "DLT" message to the "F" object.
Move to the world of lower case and no abbreviations and you get:

File.delete, Command.delete, Program.delete

What does this say? It actually says two things. First, it
says that for each of these object types (or "classes" in
Java terminology) there is a delete method that can be
called. Different things will happen depending on which
object type you're deleting.

More importantly, though, it says that you can delete an
object represented by the File class by executing its delete
method, and that you can do the same for Command and for
Program. So finally:

myFile.delete(), myCommand.delete(), myProgram.delete()

This is the essence of polymorphism: call the same method for
different objects and the underlying code will do what it's
supposed to do.

To me, it's less an issue of understanding the concept than
it is of the syntax.

DLTCMD CMD(MYCMD) vs. myCommand.delete()


Joe


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