How to sort an array of dates in descending order

Question

I have a NSDictionary that parsed to an array one of the element is date, i tried using [startimeArray sortUsingSelector:@selector(compare:)]; (starttimeArray) is my date but it only arrange ascending. how can i sort in descending order. thanks

Answer 1

You can use a comparator block

NSArray *sortedArray = [array sortedArrayUsingComparator: ^(NSDate *d1, NSDate *d2) {
    return [d1 compare:d2];
}];

to reverse the order, just swap the dates

NSArray *sortedArray = [array sortedArrayUsingComparator: ^(NSDate *d1, NSDate *d2) {
    return [d2 compare:d1];
}];

or — as compare: returns a NSComparisonResult, which is actually typedef'ed to integer _{see below} — just multiply by -1

NSArray *sortedArray = [array sortedArrayUsingComparator: ^(NSDate *d1, NSDate *d2) {
    return -1* [d1 compare:d2];
}];

---

enum {
   NSOrderedAscending = -1,
   NSOrderedSame,
   NSOrderedDescending
};
typedef NSInteger NSComparisonResult;

Answer 2

Sort the array by puting NO is ascending parameter:

NSSortDescriptor *descriptor=[[NSSortDescriptor alloc] initWithKey:@"self" ascending:NO];
NSArray *descriptors=[NSArray arrayWithObject: descriptor];
NSArray *reverseOrder=[dateArray sortedArrayUsingDescriptors:descriptors];