Question

I am running the following code to sort my array in the order of ending soonest (nearest expiry_date to [NSDate date] (now).

However, whenever I run the comparator, it has no affect, at all on the array, and all objects retain their current positions. Please can you tell me where I am going wrong?

[self.questions sortUsingComparator:^NSComparisonResult(NSDictionary * question1, NSDictionary *question2) {

     NSDate* dateq1 = [NSDate dateWithTimeIntervalSinceNow:[[question1 objectForKey:@"expiry_date"] floatValue]];
     NSDate * dateq2 = [NSDate dateWithTimeIntervalSinceNow:[[question2 objectForKey:@"expiry_date"] floatValue]];

     NSComparisonResult result = [dateq1 compare:dateq2];

     NSLog(@"%@", result == NSOrderedAscending ? @"ASC" : result == NSOrderedDescending ? @"DESC" : @"SAME");

     return result;

}];

The NSLog() returns the following:

DESC
DESC
ASC

I have tried reversing the comparison to have dateq2 in the place of dateq1 and vice versa, but the array never changes, even though the returned values do.

Answer 1

It looks like it is working to me (judging by your output), but maybe this is more succinct and therefore less error prone?

NSArray* unsorted;
NSSortDescriptor* descriptor = [NSSortDescriptor sortDescriptorWithKey: @"expiry_date" ascending: NO];
self.questions = [unsorted sortedArrayUsingDescriptors: @[ descriptor ] ];