需要帮助NSDecimalNumber

Question

我正在尝试使用我拥有的NSDecimalNumber，并将其乘以1.1。

我有这个，但它不起作用：

NSDecimalNumber *multipy = [NSDecimalNumber decimalNumberWithMantissa:1.1 exponent:0 isNegative:NO]; 
NSDecimalNumber *savings = [totalExpenses decimalNumberByMultiplyingBy:multipy];

更新

以下是整个代码，有谁知道它为什么不起作用？

NSDecimalNumber *totalExpenses = [[event.housePayment decimalNumberByAdding:event.carPayment] decimalNumberByAdding:event.loanPayment];
NSDecimalNumber *multiply = [NSDecimalNumber decimalNumberWithMantissa:11 exponent:-1 isNegative:NO];
NSDecimalNumber *savings = [totalExpenses decimalNumberByMultiplyingBy:multiply];

在乘法线处崩溃，错误为：*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UITableViewCell decimalNumberByMultiplyingBy:]: unrecognized selector sent to instance 0x5d91a60'

Answer 1

尝试：

NSDecimalNumber *multipy = [NSDecimalNumber decimalNumberWithMantissa:11 exponent:-1 isNegative:YES]; 

Answer 2

尾数需要是一个整数，所以要乘以十来调整，然后将指数减一。

即

NSDecimalNumber *multipy = [NSDecimalNumber decimalNumberWithMantissa:11 exponent:-1 isNegative:NO];