Ian Joyner wrote:
On 13/02/2006, at 4:09 PM, David Avendasora wrote:
I and a new OO programmer and I *really* appreciate everyone's advice
on OO design!
In this case, these three part types have some very specific
differences. It is not one part that changes. My application is being
built to manage the manufacturing in a bakery.
- Raw parts are sugar, flour, oil, etc. and are usually procured from
outside vendors.
- Intermediate parts are things like dough, toasted coconut and such
where an intermediate part has a Bill of Materials and requires work
within the manufacturing line to have produced.
- Finished parts things like like cookie, bar, etc. and are parts
made up of any number of Raw and/or Intermediate parts. Since they
are sold to customers they also have to have additional attributes
like UPC code, customer specific attributes.
Does this still sound like something that would work better as an
implementation of the Status Pattern, or should I stick with
Inheritance?
OK, that clarifies it and I think your inheritance design is probably
fine. Do these three kinds of things have features in common? Data
values (either attributes or typed functions) and procedures (untyped
(void) functions). What I do think you'll have is for the intermediate
and final parts, as 'has-a' relationship 'ingredients'. Make sure you
don't mix up the is-a (inheritance) with has-a (component-of)
relationships. Otherwise inheritance is fine.
Ian
Right, and I think, generally speaking and as discussed in Head First
Design Patterns, one should favor composition over inheritance.
Inheritance can lock you into design choices since no common language
allows modification of inheritance hierarchies at runtime.
So, I would design Finished as a container for Ingredients and
Ingredients as containers for RawMaterials. Using Ian's language
Finished has-A Ingredient etc.
-arturo
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list ([email protected])
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to [email protected]
