RE: Classes/Objects compared to SRVPGMs -- RPG400-L

Adam,

I completely agree, well designed programs, be they modules, service
programs or regular programs are all good for reuse and decreasing
maintenance.

What I do want to point out - and yes, I will keep on hammering about
that ;) - is that 'old fashioned' programming styles (what we are used
to and love in RPG, Cobol, C and what have you in that area) can never
be compared in functionality and use to OO programming styles with the
whole concept of inheritance and reuse through classes/objects and what
have you which is used in Smalltalk, Java, C++ and the likes.

Comparison can be used to clarify some similarities; what you have to be
wary about is that the comparison is perceived as gospel. That will
inevitably lead to grave mistakes.

Regards,

Cor

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-
bounces@xxxxxxxxxxxx] On Behalf Of Adam Glauser
Sent: donderdag 19 juni 2008 15:04
To: rpg400-l@xxxxxxxxxxxx
Subject: Classes/Objects compared to SRVPGMs

Takken, Cor wrote:

RPG IV is not an object oriented language, Java is. Classes

represent

runnable code which can only be used once instantiated as an object
(barred static methods), modules and service programs can be

compared

to

static (so class-level) methods. Classes are abstract descriptions

objects, objects are instantiations of classes and represent a class

in

a certain state which can behave in a predescribed way (the code in

the

class) as is fit for that state. A module is not a class, a module

a

stream of code which can be called from the outside to perform some
functionality and that is it.

<snip>

[W]hile I appreciate
that there are ways to simulate [instantiation-like] behaviour (e.g.

copy the same

module to different locations or by renaming the compiled object)

that

would still be a simulation and not have the same flexibility as

object

instantiation. The whole programming concept of RPG is different

from

Object Oriented (or close to Object Oriented) languages as Java,

C++,

C#, etc. You can't compare the two except on the bare line to line

code

basis (comparing if-statements etc.).

I certainly agree with you that comparisons between classes/objects

and

service programs can only go so far. I also agree about the
flexibility
that the OO model provides.

I do however, think that there is some value in the comparison in that
both structures help to simplify implementation modular designs, and
therefore can be used to accomplish some of the same goals. Well
designed service programs can provide encapsulation and ease reuse
(thereby reducing maintenance efforts).
--
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