Re: Newbie Key Value-coding and Subclasses Question
Re: Newbie Key Value-coding and Subclasses Question
- Subject: Re: Newbie Key Value-coding and Subclasses Question
- From: David Avendasora <email@hidden>
- Date: Thu, 9 Feb 2006 16:38:57 +0000
Arturo,
On question 1, I am currently testing for what type of Class it is by
reading my PartType field using:
if (((String) valueForKeyPath("part.partType.partTypeName")).equals
("Finished Part")) {...}
and this works just fine, but my understanding was that instanceof is
a better OO way of doing things - especially since the string
partTypeName is a value from a DB field which could potentially change.
On the second question, The problem is that "Label" is not related to
"Finished", but to it's superclass "Part". Once I know that the
"Part" I'm dealing with is a "Finished" (subject of question 1) then
how do I call a method from the "Finished" subclass using key value-
coding? valueForKeyPath("part.unitQuantity") does not work because
unitQuantity is not a attribute of "Part" it is an attribute of
"Finished".
Dave
On Feb 9, 2006, at 4:17 PM, Arturo Perez wrote:
David Avendasora wrote:
Hi.
I have a relationship from Label to Part (toOne)
Part has three subclasses: Raw, Intermediate and Finished. All of
these (Part, Raw, Intermediate and Finished) are all
EOGenericRecord classes right now.
I'm running into two problems
1) How do I perform an instanceof to determine what subclass of
Part takeStoredValueForKey("part") returns when run on a Label
object? Do I have to generate the custom classes first for Part
and it's subclasses?
2) How do I call subclass-specific methods with key value-coding
when the relationship is to the superclass? I have no problem
executing superclass-specific methods using valueForKeyPath
("part.partDescription"), but I want something along the lines of
valueForKeyPath("finished.unitQuantity") (unitQuantity is an
attribute of the Finished subclass of Part)
Well, instanceof in an OO design is generally considered bad
practice. You may want to reconsider if your design requires it.
If you really do need to know what something is I think you can do
something like getting the EODescription/EOClassDescription of the
EOGenericRecord and one of the attributes is the name you've given it.
What's the problem you're running into with the second thing? If
you have a relationship to something and you do what you've written
it should just work.
-arturo
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