Re: Predicates: Trying to filter against max()
Re: Predicates: Trying to filter against max()
- Subject: Re: Predicates: Trying to filter against max()
- From: Sean Murphy <email@hidden>
- Date: Wed, 5 Apr 2006 23:43:20 -0400
On Apr 5, 2006, at 5:54 PM, Fritz Anderson wrote:
I have an entity, Bank, which contains Entrys in its relationship
"table". Entry has an int attribute, "ordinal".
I want to find the Entry with the highest ordinal. I can do this by
sorting an array derived from the set returned for the "table"
relationship, and taking the last one; but it seems to me I should
be able to filter the array with an NSPredicate like "ordinal == max
(ordinal)".
Hey Fritz,
Using the NSPredicate class is usually such an awesome and amazingly
simple way to filter an array, but in your case maybe you can utilize
a Key-Value Coding array operator. I'm not sure if this suggestion
is what you were looking for, and you probably have even thought of
it already, but since the predicate language syntax is giving you so
much trouble, try something like this:
[self valueForKeyPath:@"email@hiddenal"];
This does assume allEntries is a KVC Compliant member of the current
class, which might not be the approach you had in mind. This at
least will give you another alternative (maybe!), instead of choosing
between using predicates or sorting the array and picking out the
last item. I'm not too familiar with using more advanced predicate
queries, otherwise I'd try to help find a solution more in-line with
your current code.
Also, I should mention that I'm actually reading your Step Into Xcode
book right now (every morning with breakfast)..great work! It's
definitely a nice addition to my library of Mac programming books,
and I've picked up quite a bit from reading it.
I Hope this was of some help, but if not I at least was able to give
you a "thumbs up" on the book!
-Sean
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