On 07-feb-2011, at 16:29, Ken Thomases wrote: > On Feb 7, 2011, at 8:56 AM, Michael Crawford wrote: > >> I'm trying to implement a feature where I sort a cross-section of music from >> multiple genres with up to two different keys, where the items with a genre >> matching the first key appear first in the collection and items with a genre >> matching the second key appear after the first group in the collection. All >> songs with a genre not matching the first or second keys can be in any order >> following the first two groups. >> >> So I took a look at NSSortDescriptor but it is not apparent to me how I >> would accomplish my goal with this class. If I sort with it based on the >> genre key, will basically sort them in alphabetical ascending or descending >> order, not what I want. > > Here are two possible approaches: > > 1) Implement a synthetic property which is more amenable to the sort ordering > you want. Something which returns 0 for the first genre, 1 for the second, > and 2 for all others, for example. > > 2) Implement a custom comparator method that compares the existing genre > property in the manner you want: the first genre equal to itself but coming > before all others; the second genre coming after the first, equal to itself, > and coming before the remaining genres; all other genres coming after the > first two but unordered with respect to each other. > > Either or both of these methods could be implemented in a category if that > makes things easier. >
Or subclass the NSSortdescriptor and implement - (NSComparisonResult)compareObject:(id)object1 toObject:(id)object2 Cool Runnings, Erne. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
