NSDecimalNumber - Propagation of Strangeness

Question

ExclusivePrice, quantity - NSDecimalNumbers.

NSDecimalNumber *price = [exclusivePrice decimalNumberByMultiplyingBy:quantity];
NSLog(@"%@ * %@ = %@", exclusivePrice, quantity, price);

Result:

2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = -0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007169919476068871316457914368

What I expected:

2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = 130

Can someone explain this please?

Edit:

Full play:

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterDecimalStyle];
NSDecimalNumber *n2 = (NSDecimalNumber *)[formatter numberFromString:@"2"];
NSDecimalNumber *n1 = (NSDecimalNumber *)[NSDecimalNumber numberWithInt:65];
NSDecimalNumber *n3 = [n1 decimalNumberByMultiplyingBy:n2];
NSLog(@"%@ * %@ = %@", n1, n2, n3);

Answer 1

I found the answer: According to How to use NSDecimalNumber? I cannot easily convert NSNumber and NSDecimalNumber. To convert from one to another, I need to do:

NSDecimalNumber *n2 = [NSDecimalNumber decimalNumberWithDecimal:
                              [[formatter numberFromString:@"2"] decimalValue]];

It would be nice if NSNumberFormatter had the decimalNumberFromString: method.

Answer 2

It seems to work for me.

NSDecimalNumber * n1 = [NSDecimalNumber decimalNumberWithString:@"65"];
NSDecimalNumber * n2 = [NSDecimalNumber decimalNumberWithString:@"2"];

NSDecimalNumber * res = [n1 decimalNumberByMultiplyingBy:n2];

NSLog(@"%@ * %@ = %@", n1, n2, res);

Conclusion:

2010-04-05 08:40:42.812 x[24301] 65 * 2 = 130