Objects and such

From: Buck

I write my own commands all the time, am comfortable with converting C
structures into RPG DS specs and in my vanity, I like to think I have a
handle on the basics of OO.

None of that prepared me for polymorphism.

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