How to sort NSArray of NSDictionary items

Question

I have an NSArray of NSDictionaries which I would like to sort and remove duplicates from. The issue I am having is the NSDictionary contains two elements startYear and finishYear so I have an NSArray of Dictionary values that I would like to sort using startYear and finishYear.

The NSDictionary looks like this, They both contain string values.

starYear
finishYear

The values that are contained in both look like this -

(startYear / finishYear)
------------------------
(0 - 1999)
(1999 - 0)
(1999 - 2000)
(2001 - 2008)
(2000 - 2010)
(0 - 1999)
(0 - 2006)

should look like this -

(startYear / finishYear)
------------------------
(0 - 1999)
(1999 - 0)
(1999 - 2000)
(0 - 2006)
(2000 - 2010)
(2001 - 2008)

As you can see any repeating values have been removed. If startYear is 0 then that values is sorted by finishYear. If startYear and finishYear are avalible then its sorted into its startYear and then ordered according to finish year.

I am at a complete loss on how to even approach this, I have read up about sets etc.. But I just have no idea on how to sort according to the two elements in the NSDictionary.

I hope this is enough information to get some help, suggestions code examples anything to get me onto solving this would be greatly appreciated.

You can easily sort on the startYear first, then the finishYear or the reverse with the technique suggested by @Skotch but yours seems to be neither. How would you handle the range 1996-2012 for example? — aLevelOfIndirection
1996 - 2012 would appear first in this instance. if its 1996 - 0 that would appear before your example.. if its 0 - 2012 it would appear later down the array. — C.Johns

Skotch Skotch · Accepted Answer · 2013-04-25T21:51:27

For this you can use NSOrderedSet or NSArray. Let's assume an array, which you sort using a comparator. Something like this:

NSString const * kStartYear = @"startYear";
NSString const * kFinishYear = @"finishYear";

NSArray *unsortedArray = @[
                           @{kStartYear:@0,
                             kFinishYear:@1999},
                           @{@"startYear":@1999,
                             kFinishYear:@0},
                           @{kStartYear:@1999,
                             kFinishYear:@2000},
                           @{kStartYear:@2001,
                             kFinishYear:@2008},
                           @{kStartYear:@2000,
                             kFinishYear:@2010},
                           @{kStartYear:@0,
                             kFinishYear:@2006},
                           ];

NSArray *sortedArray = [unsortedArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
    NSDictionary *dictA = a;
    NSDictionary *dictB = b;

    NSNumber *startYear1 = dictA[kStartYear];
    NSNumber *startYear2 = dictB[kStartYear];
    return [startYear1 compare:startYear2];

    // Put in more logic for your comparison
}];


NSLog(@"sorted: %@", sortedArray);

Updated: more correct code

How to sort NSArray of NSDictionary items

1 Answers