Question

I have a NSMutableArray with objects of type NSMutableDictionary,

the NSMutableDictionary contains 2 keys

-Airlines (string)

-Rating (integer)

I have an NSMutableArray with all the objects and what i need is to Sum the rating of all the airline companies repeated objects, an example:

Airline  Rating

  A         2

  B         3

  B         4

  C         5

The end result array will be the A = 2, C = 5 and the Sum of B´s that is equal to 7.

My code so far:

for (int i = 0; i < arrayMealRating.count; ++i) {
         NSMutableDictionary *item = [arrayMealRating objectAtIndex:i];
         NSLog(@"item=%@",item);
         for (int j = i+1; j < arrayMealRating.count; ++j)
         {
           if ([[item valueForKey:@"Airline"] isEqualToString:[arrayMealRating objectAtIndex:j]]){
                NSMutableDictionary *item = [arrayMealRating objectAtIndex:j];
                NSMutableDictionary *item1 = [arrayMealRating objectAtIndex:i];
                NSInteger auxCount =  [[item valueForKey:@"setMealRating"] integerValue] + [[item1 valueForKey:@"setMealRating"] integerValue];

                NSMutableDictionary *aux = [NSMutableDictionary dictionaryWithObjectsAndKeys:[item valueForKey:@"Airline"], @"Airline"
                                                        ,[NSString stringWithFormat:@"%d",auxCount], @"setMealRating"
                                                        ,nil];
                NSLog(@"aux=%@",aux);
                [arrayMealRating replaceObjectAtIndex:i withObject:aux];

            }
         }
   }

A bit messy i know but i dont know how to work with NSMutableDictionary, any help will be much appreciated, Thanks in Advance!

Answer 1

Incase you dont want to change how your storing the data, heres how you would do it using key-value coding. Heres the dirrect link to the documentation for @distinctUnionOfObjects and @sum.

// Get all the airline names with no duplicates using the KVC @distinctUnionOfObjects collection operator
NSArray *airlineNames = [arrayMealRating valueForKeyPath:@"@distinctUnionOfObjects.Airline"];

// Loop through all the airlines
for (NSString *airline in airlineNames) {

    // Get an array of all the dictionaries for the current airline
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(Airline == %@)", airline];
    NSArray *airlineMealRating = [arrayMealRating filteredArrayUsingPredicate:predicate];

    // Get the sum of all the ratings using KVC @sum collection operator
    NSNumber *rating = [airlineMealRating valueForKeyPath:@"@sum.Rating"];
    NSLog(@"%@: %@", airline, rating);
}

This gives the following output

A: 2
B: 7
C: 5