How to sort NSMutableArray of date objects

Question

I'm doing some small work on sorting the date strings in the NSMutableArray, i'm getting the array from the sqlite db. If you print the array it is showing like this

date strings are ( "2011-05-01", "2011-02-01", "2012-01-08", "2012-05-08", "2010-01-09 )

I want to show the dates in ascending order. Please help me out guys..... I'm newbie to objc..

Campanula

Answer 1

First you should convert all date Strings (which is NSString) objects to NSDate objects and then sort these dateObjects.

I believe you have dateArray containing all those strings.

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

OR

NSArray *reverseOrderUsingComparator = [dateArray sortedArrayUsingComparator: 
                                       ^(id obj1, id obj2) {
                                           return [obj2 compare:obj1];
                                       }];

Buoy

The date format he showed in his question will sort correctly even as strings. – Bagworm

That's unnecessary, he can just arrange the strings as they are right now. – Crutchfield

Nice thanks man.... I used ur second one, but it is showing the array objects in descending order...how can i do it for ascending – Campanula

Answer 2

If your dates are really strings in the format YYYY-mm-dd, as in your question, then this will sort them in ascending order:

[arrayOfDates sortUsingSelector:@selector(compare:)];

That will also work if your dates are actually NSDate objects.

If you want to create a sorted copy of the array:

NSArray *sortedArray = [arrayOfDates sortedArrayUsingSelector:@selector(compare:)];

Bagworm

Answer 3

Sorting should be done, imo, by the database, in general. sqlite3 does support order by.

Benzine