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..

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];
                                       }];

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:)];

Answer 3

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