RE: [Re: RPGILE V4.3 Gotcha] and OO design

  I'm in a mood for _serious_ ranting today.  If I have enough time I may
even get into pomposity.<g>

This example shows how hard it is to design something to be extensible and
how easy it is to misuse or misunderstand a theoretical approach to problem
solving.  

Object oriented design is a really cool idea.  It's also been promoted as a
panacea.  Unfortunately, it's like any other tool, you have to think about
it before you use it, and you have to do your best to use it correctly.  One
of my teachers in school gave us a list of criteria for developing recursive
algorithms.  Rule 1 was "It has to work."  

I know I've skipped rule 1 before, and I've suffered the consequences every
time.  No tool can protect you from yourself.

    
> -----Original Message-----
> From: boldt@ca.ibm.com [mailto:boldt@ca.ibm.com]
> Sent: Friday, October 08, 1999 6:13 AM
> To: RPG400-L@midrange.com
> Subject: Re: [Re: RPGILE V4.3 Gotcha]
> 
> 
> 

/*               Big Snip                                         */


> That section in that book illustrates the potential for overuse of
> inheritance.  For example, many OO texts use the example of
> employees in a company.  Using inheritance, you could design a base
> class called Employee.  You could then have derived classes called
> Manager and VicePresident, such that a Manager "is a" Employee, and
> a VicePresident "is a" Manager.  But what happens when an employee
> is promoted?  In this case, a better design would use "has a"
> relationships.  For example, an Employee "has a" Role, which could
> be regular employee, manager, or vice-president.  To promote an
> employee, simply assign a new Role to her.
> 
> 
> 
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