iphoneobjective-cnsdecimalnumber

Turn a NSDecimalNumber negative


I am looking for a way to turn a NSDecimalNumber negative by multiplying by -1.

/* decNumber is the one I would like to turn negative */
NSDecimalNumber *decNumber = [values objectAtIndex:billIndex];

NSDecimalNumber *minusOne = [[NSDecimalNumber alloc] initWithInt: -1];
finalValue = [[NSDecimalNumber alloc] initWithDecimal: [[decNumber decimalNumberByMultiplyingBy: minusOne] decimalValue]];

This works but it feels like it's just too much for such a simple logic. Can you think of a better way to achieve this?


Solution

  • You could use NSDecimalNumber>>decimalNumberWithMantissa:exponent:isNegative to generate -1 more concisely.

    /* Answers (aDecimal x -1) */
    NSDecimalNumber* negate(NSDecimalNumber *aDecimal) {
        return [aDecimal decimalNumberByMultiplyingBy:
                        [NSDecimalNumber decimalNumberWithMantissa: 1
                                                          exponent: 0
                                                        isNegative: YES]];
    }