On Apr 7, 2008, at 8:26 AM, Bob Stuart wrote:
At 11:20 AM -0400 4/7/08, David Avendasora wrote:
On Apr 7, 2008, at 10:36 AM, Mike Schrag wrote:
I'd expect the instanceof check will be much more efficient than
catching an exception.
By far ...
From an OO design point of view, I'd add a billsOfMaterial()
method to the Part class that simply returns NSArray.emptyArray.
ManufacturedPart will then override this to return the correct
result for a ManufacturedPart.
Ew gross ...
By far one of my favorite technical arguments.
If it's not an attribute of all Parts, then from an OO design
standpoint it shouldn't be on Part. I agree if your argument is
based on "the convenience of being able to call billsOfMaterial on
the entire array," though.
Yeah, I'm getting the impression that there's no really "ungross"
OO way to do this. I think this and instanceOf are equally "gross"
because if I add other classes that have a billsOfMaterial()
relationship, then I'd have to remember to come here and add it to
the list of things instanceOf checks.
I think I'll go with adding the billsOfMaterial() method to Part
because then I can use this same logic in more places without
having to write the instanceOf check every time.
If you want to avoid adding the method to Part you could create an
interface and have the instance of check that. Then only the classes
that have this would implement the interface. That way you only have
to change things when you make the new class and only in the class
not however many places you might do the instanceof check.
Using instanceof on a member of an inheritance hierarchy is a bad code
smell. It is the code's ways of telling you that your design is
wrong. IMO.
Chuck
--
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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