Sort NSArray of date strings or objects

Question

I have an NSArray that contains date strings like this: "Thu, 21 May 09 19:10:09 -0700"

I need to sort the NSArray by date. I thought about converting the date string to an NSDate object first, but got stuck there on how to sort by the NSDate object.

Thanks.

Answer 1

Once you have an NSDate, you can create an NSSortDescriptor with initWithKey:ascending: and then use sortedArrayUsingDescriptors: to do the sorting.

Answer 2

You can use sortedArrayUsingFunction:context:. Here is a sample:

NSComparisonResult dateSort(NSString *s1, NSString *s2, void *context) {
    NSDate *d1 = [NSDate dateWithString:s1];
    NSDate *d2 = [NSDate dateWithString:s2];
    return [d1 compare:d2];
}

NSArray *sorted = [unsorted sortedArrayUsingFunction:dateSort context:nil];

When using a NSMutableArray, you can use sortArrayUsingFunction:context: instead.

Answer 3

Store the dates as NSDate objects in an NS(Mutable)Array, then use -[NSArray sortedArrayUsingSelector: or -[NSMutableArray sortUsingSelector:] and pass @selector(compare:) as the parameter. The -[NSDate compare:] method will order dates in ascending order for you. This is simpler than creating an NSSortDescriptor, and much simpler than writing your own comparison function. (NSDate objects know how to compare themselves to each other at least as efficiently as we could hope to accomplish with custom code.)

Answer 4

thanks - its work

Answer 5

If I have an NSMutableArray of objects with a field "beginDate" of type NSDate I am using an NSSortDescriptor as below:

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"beginDate" ascending:TRUE];
[myMutableArray sortUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];