Question

NSString * str = @"ABCDEFGHILMN";

NSDictionary *dictOdd = [[NSDictionary alloc] initWithObjectsAndKeys:
                          [NSNumber numberWithInt:0], @"A",
                          [NSNumber numberWithInt:1], @"B",
                          [NSNumber numberWithInt:2], @"C",
                          [NSNumber numberWithInt:3], @"D",
                           ...............................
                          nil];

NSDictionary *dictEven = [[NSDictionary alloc] initWithObjectsAndKeys:
                          [NSNumber numberWithInt:1], @"A",
                          [NSNumber numberWithInt:0], @"B",
                          [NSNumber numberWithInt:5], @"C",
                          [NSNumber numberWithInt:7], @"D",
                           ...............................
                          nil];

int sum  = 0;   
for (int i=1; i < [str length]; i++){
    if(i % 2){
        sum += [dictPair objectForKey:str[i]];
    }else{
        sum += [dictEven objectForKey:str[i]];
    }
}

I have created 2 dictionary for storage int numbers / letters, each letter have a int value.

I would make the sum of int numbers in relation to my str value, but i don’t know how assign objectForKey:str[i]];

Answer 1

I think you are looking for characterAtIndex: which would leave you with

sum+=[[dictPair objectForKey:[NSString stringWithFormat:@"%C",[str characterAtIndex:i]]] intValue];