How to convert elements of NSMutableArray (NString) to NSNumber and add them up?

Question

Ok so I have NsMutable array with Strings which are in format:

  32,45,54,5550 etc.

What is the easiest way to convert all these strings to nsnumber and also get the sum of entire array.

Answer 1

You can use the KVC collection operator @sum to get the summation of all number strings stored in an array

NSArray *numberStrings = @[@"32",@"45",@"54",@"5550"];
NSNumber* sum = [numberStrings valueForKeyPath: @"@sum.self"];
NSLog(@"%@", sum);

output: 5681

For simple strings it works. But caution: in localization there might be traps. There-for I would still suggest to use a NSNumberFormatter to create real NSNumber objects, store them in another array and use @sum on that.

---

_{Thanks Bryan Chen for make me test.}

---

To raise the awareness for problems that might lie in localization, I want to share this experiment with you:

In German we use , to separate the decimal digits, where as we use the . to group long numbers in thousands.

So if the numberString array might be filled with german formatted numbers, it might look like @[@"32,5", @"45", @"54", @"5.550,00"]. The sum of this is 5681.5, but if we do not alter the code, it will not fail, but worse — miscalculate: 136.55. It just ignored everything past a comma and treated . as decimal separator.

Lets use a NSNumberFormatter to fix it:

My system is set to german locale

NSNumberFormatter *nf = [[NSNumberFormatter alloc] init];
nf.locale = [NSLocale currentLocale];
[nf setGroupingSize:3];
nf.usesGroupingSeparator= YES;

NSArray *numberStrings = @[@"32,5", @"45", @"54", @"5.550,00"];
NSMutableArray *numbers = [@[] mutableCopy];

for (NSString *s in numberStrings) {
    NSNumber *n = [nf numberFromString:s];
    [numbers addObject:n];
}


NSNumber* sum = [numbers valueForKeyPath: @"@sum.self"];

NSLog(@"%@", sum);

it prints correctly 5681.5.

Answer 2

NSArray *array = @[ @"1,2", @"3,4" ];
NSUInteger sum = 0;
for (NSString *str in array)
{
    for (NSString *num in [str componentsSeparatedByString:@","])
    {
        sum += [num intValue];
    }
}

or

NSArray *array = @[ @"1", @"3" ];
NSUInteger sum = 0;
for (NSString *num in array)
{
    sum += [num intValue];
}