Re: NSArray (unique Items matching x)
Re: NSArray (unique Items matching x)
- Subject: Re: NSArray (unique Items matching x)
- From: Jens Alfke <email@hidden>
- Date: Wed, 10 Feb 2010 18:11:52 -0800
On Feb 10, 2010, at 1:45 PM, Trygve Inda wrote:
> iTunes seems to do this with the column browser... Eg when you select
> "Classic Rock", it pulls up a list of Artists without duplicates in the
> list... And does it very fast.
But keep in mind that iTunes is a Carbon app, not Cocoa.
> It seems like a Predicate is working here... When one clicks "Classic Rock",
> that is added to the predicate as Genre="Classic Rock", but then how does it
> extract the list of Artists from the master array since it doesn't want
> duplicates?
You're asking about iTunes' implementation, which we have no idea about. It seems to use some kind of custom database. What you're describing is a typical sort of database query (in SQL it would be like "select distinct artist from ...").
At a low level, in your code you could use an NSMutableSet to collect together the artist results, which would remove duplicates. I'm sure this would get awkward to work with, though.
Basically I think you're running into the limitations of your very simple data structure. You could come up with something more complex, or you could start using CoreData and let it manage the data storage and querying for you.
—Jens_______________________________________________
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