Question

I have an array that contains a custom class of mine called ‘Game’. Each ‘Game’ contains an NSDate. I would like to reorder my Array based on the dates so that they are in order from newest to oldest. How could I do that? Also, my class ‘Game’ contains an NSString. How could I reorder my Array so that the games are alphabetized?

Answer 1

There’s a REALLY simple way to do this, and that’s with an NSSortDescriptor:

NSArray *games = ...; //your unsorted array of Game objects
NSSortDescriptor *sortByDateDescending = [NSSortDescriptor sortDescriptorWithKey:@"date" ascending:NO];
NSArray *descriptors = [NSArray arrayWithObject:sortByDateDescending];

NSArray *sortedGames = [games sortedArrayUsingDescriptors:descriptors];

Apple’s already written the sorting code. It just needs to know what properties to sort by. That’s what an NSSortDescriptor encapsulates. Once you’ve got one, simply give it to the array, and the array give you back a sorted version. (Alternatively, if you have an NSMutableArray, you can sort it in-place using -sortUsingDescriptors:)