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

Swift 3.0

For anyone using swift 3.0 this DateHelper will save u some headache.

   filteredLogs.sort(by: {
        let firstElement = $0.timeStamp! as Date
        let secondElement = $1.timeStamp! as Date
        return firstElement.compare(.isEarlier(than: secondElement))
    })

The above code is a snippet from one of my projects. It uses the helper class to sort my logs with most recent dates at the left of the array. The $ sign is a positional parameter

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];

Answer 3

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 4

I'd use the built-in reverseObjectEnumerator method of NSArray

startimeArray = [startimeArray sortUsingSelector:@selector(compare:)];
startimeArray = [[startimeArray reverseObjectEnumerator] allObjects];

It's useful when you need the array sorted in ascending and descending order, so you can easily go back to the previous sort.

Answer 5

There is the swift solution for the checked solution :

let sortedArray = randomArray.sortedArrayUsingComparator { (d1, d2) -> NSComparisonResult in
    return (d1 as! NSDate).compare(d2 as! NSDate)
}

Answer 6

In the Class where the Array elements are being initialized.

-(NSComparisonResult) compareArray: (id) element {
    Return [ArrayElement compare: [element ArrayElement]];
}



-(NSComparisonResult) compareArrayReverse: (id) element {
    Return [[element ArrayElement] compare: ArrayElement];
}

Then in the Class where your startimeArray is initialized:

@synthesize ArrayName;


-(void) sort: (BOOL) sel {
    if (sel) {
        [ArrayName sortUsingSelector: @selector(compareArray:)];
    } else {
        [ArrayName sortUsingSelector: @selector(compareArrayReverse:)];
    }    
}

Then in the main():

// Sort the array. sort = TRUE - ascending order, sort = FALSE - descending order.

[startimeArray sort: FALSE];