Constants imply DP (was: Question on last Monday's meeting)

[Mark Windholtz <windholtz@xxxxxxxxx>]

Mitchell, John  wrote:
> 
> If a constant is needed by more than one
> class, what is the alternative?  

 The question is WHY is it needed by one or more classes?
 What is the behavior that needs a constant?
 Most likely some "if" statement or "switch" is using it
 to choose a list of possible behaviors.
 To contain the spread of this kind of conditional logic
 is why OO was invented.

 A constant is data.
 That data is used by other things, called processes.
 When a single process needs the constant,
     move the constant to the place it is used 
     and encapsulate it from the world.

 When multiple places need the constant, ask why.
 Most likely you need a new Object that has behavior 
 that uses that constant and is called by the various
 places that originally directly accessed the constant.

 If your frameworks require you to program with lots
 of constants question your choice of frameworks.

 One step is to put the shared behavior and constant 
 into a global object.

 Global objects are called Singletons.
 They also cause trouble, but are still better than 
 global data (ie. constants) because at least they provide 
 behavior not just data.

 Config files can also be a source of global constant data.
 They also should be encapsulated inside objects.

> Feel free to refer me to an article or something.
> 

Sorry I havn't written it up yet.

-- 
Regards,
-Mark