sum quantity of dictionaries in array

Question

I have a NSArray containing a list of NSDictionary. Like:

NSArray *array = ...;
NSDictionary *item = [array objectAtIndex:0];
NSLog (@"quantity: %@", [item objectForKey: @"quantity"]);

How can I sum all the quantities contained in all dictionaries of the array?

sunkehappy · Answer 1 · 2013-08-01T14:15:06.940

8

I think you can try KVC

NSMutableArray *goods = [[NSMutableArray alloc] init];
NSString *key = @"quantity";

[goods addObject:@{key:@(1)}];

[goods addObject:@{key:@(2)}];

[goods addObject:@{key:@(3)}];

NSNumber *sum = [goods valueForKeyPath:@"@sum.quantity"];
NSLog(@"sum = %@", sum);

edited Aug 01 '13 at 14:15

answered Oct 09 '12 at 00:58

sunkehappy

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You're updating the same dictionary and adding it 3 times, so the sum will be 9, when you'd expect 6. You need to create a new dictionary in each case, like `[goods addObject:@{@"quantity": @1}];` – Christopher Pickslay Aug 01 '13 at 07:17

score 2 · Answer 2 · answered Oct 09 '12 at 00:24

2

If you call valueForKey: on an array it gives you an array of all the values for that key, so [array valueForKey:@"quantity"] will give you an array which you can loop over and sum all the values.

answered Oct 09 '12 at 00:24

rdelmar

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It's a so great way to get the array from each dictionary in the original array! Thank you very much! – sunkehappy Oct 09 '12 at 01:00

score 0 · Answer 3 · answered Oct 10 '12 at 06:56

0

NSMutableArray *quantityArray = [item objectForKey: @"quantity"];
int total =0;
for(int i=0;i<[quantityArray count];i++)
{
  total+= [quantityArray objectAtIndex:i];
}

answered Oct 10 '12 at 06:56

Durga Vundavalli

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sum quantity of dictionaries in array

3 Answers3