将 NSDecimalNumber 转为负数

我正在寻找一种方法来扭转NSDecimalNumber乘以负数-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]];

这可行，但感觉对于如此简单的逻辑来说有点太多了。你能想出更好的方法来实现这一目标吗？

你可以使用NSDecimalNumber>>decimalNumberWithMantissa:指数:isNegative http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSDecimalNumber_Class/Reference/Reference.html%23//apple_ref/doc/uid/20000179-decimalNumberWithMantissa_exponent_isNegative_更简洁地生成-1。

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