How does DecimalNumberByAdding work?

Question

I have a situation which I need to add two NSDecimals and this is the code that I have:

NSDecimalNumber *total = [[NSDecimalNumber alloc] initWithString:@"0"];
for (Product* product in cartItems) {
    NSDecimalNumber *prodPrice = [[NSDecimalNumber alloc] init];
    prodPrice = product.price;
    total = [total decimalNumberByAdding:prodPrice];
}
return total;

It is completely working when I try to add two numbers such as 0.01 and 0.02 and it is giving me the 0.03.

But when I use a whole number it doesn't work. As an example when I try to add 0.01 and 1, it give me a negative number as a result. Can anyone help me with this issue?

Thanks

There is a big difference between NSDecimalNumber and NSDecimal... — Hjalmar, Sep 13 '12 at 16:02
How are you checking that product.price is what you think it is and how are you examining the final total? Also what is the negative number you get? — JeremyP, Sep 13 '12 at 16:05
I'm debugging it in the loop and the negative number is -0.000000... — MaryamAyd, Sep 13 '12 at 16:07
Toss in a NSLog of both total and prodPrice, run your test, and add the logging output to the question. BTW, the alloc/init of prodPrice is completely useless. — Jody Hagins, Sep 13 '12 at 17:47

score 1 · Answer 1 · answered Sep 13 '12 at 19:11

1

I modified your loop slightly. The assignment productPrice = product.price is surely wrong in your code. Look at this:

NSArray *cartItems = [NSArray arrayWithObjects:@"1", @".01", nil];
NSDecimalNumber *total = [[NSDecimalNumber alloc] initWithString:@"0"];

for (NSString *price in cartItems) {
    NSDecimalNumber *prodPrice = [[NSDecimalNumber alloc] initWithString:price];
    total = [total decimalNumberByAdding:prodPrice];
}
NSLog(@"Total: %@", total);

returns

 2012-09-13 15:04:03.815 Searcher[69779:f803] TotalL 1.01

answered Sep 13 '12 at 19:11

David H

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This solution works fine but it's not working in some specific situations. – MaryamAyd Sep 14 '12 at 08:26
For example when I add 1 and 1.06 it shows me 1.05 as a result which is wrong! – MaryamAyd Sep 14 '12 at 08:27
So if I take the loop above and make the two numbers 1 and 1.06 the result will be 1.05? I think not. – David H Sep 14 '12 at 11:51

How does DecimalNumberByAdding work?

1 Answers1