Objective-c Sort Key array within array

Question

Assuming I have an NSMutableArray which is loaded from file:

searchTermsArray = [[NSMutableArray alloc] initWithContentsOfFile: yourArrayFileName];

inside this array items are key objects

for (int i=0; i<[searchTermsArray count]; i++) {
            NSLog(@"for array item %d: %@ - %@",i,[[searchTermsArray objectAtIndex:i] objectForKey:@"title"], [[searchTermsArray objectAtIndex:i] objectForKey:@"theCount"] );
        }

(which means that each array element (item) has 2 keys values:

searchTermsArray[0] = title (string) , theCount (also a string, but made out of integers)

Question: how should I sort "searchTermsArray" array from higher to lower based on "theCount" value?

(I am looking at the following code but it is not fitting the structure/syntax)

NSSortDescriptor *Sorter = [[NSSortDescriptor alloc] initWithKey:@"title" ascending:NO];
        [searchTermsArray sortUsingDescriptors:[NSArray arrayWithObject:Sorter]];
        [Sorter release];

Deepak Danduprolu · Accepted Answer · 2011-06-20 14:28:20Z

3

Shouldn't you be sorting based on theCount key?

NSSortDescriptor * descriptor = [NSSortDescriptor sortDescriptorWithKey:@"theCount" ascending:NO];
[searchTermsArray sortUsingDescriptors:[NSArray arrayWithObject:descriptor]];

answered Jun 20, 2011 at 14:28

Deepak Danduprolu

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Comments

Abizern · Accepted Answer · 2011-08-14 11:48:10Z

2

I am not sure if there is a better way to do so. But this thing works.

NSInteger intSort(id param1, id param2, void *context) {

    NSDictionary *dict1 = (NSDictionary *)param1;
    NSDictionary *dict2 = (NSDictionary *)param2;

    NSInteger dict1KeyCount = [[dict1 objectForKey:@"count"] intValue];
    NSInteger dict2KeyCount = [[dict2 objectForKey:@"count"] intValue];

    if (dict1KeyCount < dict2KeyCount) {
        return NSOrderedAscending;
    }else if (dict1KeyCount > dict2KeyCount) {
        return NSOrderedDescending;
    }else {
        return NSOrderedSame;
    }
}


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.

- (void)viewDidLoad {
    NSMutableArray *array = [[NSMutableArray alloc] initWithObjects:[NSDictionary dictionaryWithObjectsAndKeys:@"two", @"title", @"2", @"count", nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"three", @"title", @"3", @"count", nil],
                                [NSDictionary dictionaryWithObjectsAndKeys:@"one", @"title", @"1", @"count", nil], nil];

    NSArray *sortedArray = [array sortedArrayUsingFunction:intSort context:NULL];

    for (NSDictionary *dict in sortedArray) {
        NSLog(@"%d", [[dict objectForKey:@"count"] intValue]);
    }

    [super viewDidLoad];
}

edited Aug 14, 2011 at 11:48

Abizern

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answered Jun 20, 2011 at 14:18

user745098

4 Comments

user745098 Over a year ago

Ok, and if you want to sort in descending order, then just swap NSOrderedAscending and NSOrderedDescending in the intSort function.

chewy Over a year ago

thanks for the answer, can u be slightly clearer regarding the params and context ?

user745098 Over a year ago

It is basically the comparator function, which will define how your array will get sorted. We take parameters as id so that it supports all sort of objects. Since, your array contains Dictionary, we cast it to it and further tell the comparator function how the comparison has to be done. Also, please note that deepak's answer works too. It is short and nice.

chewy Over a year ago

Thanks pratikshabhisikar I appreciate the time and effort.

Fervus · Accepted Answer · 2011-06-20 14:25:06Z

0

The NSSortDescriptor is usually used to sort objects of a class. You pass the name of the property in that class to be compared with others. Since what you have in your array actually seems to be a NSDictionary, the NSSortDescriptor might not be the best way to approach this problem. Besides, your objects in the dictionary must have a type, so I would try to sort the array myself in one of the classic methods if I were you.

answered Jun 20, 2011 at 14:25

Fervus

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