Rounding with NSDecimalNumberBehaviors

gistfile1.txt

// sample
//let amountNumberBehaviors = AmountNumberBehaviors()
//let result = amountNumberBehaviors.round(value: value, style: .decades)

class AmountNumberBehaviors: NSDecimalNumberBehaviors {
    
    var badException = false
    
    func roundingMode() -> NSDecimalNumber.RoundingMode {
        return .up
    }
    
    func scale() -> Int16 {
        return 0
    }

    func exceptionDuringOperation(_ operation: Selector, error: NSDecimalNumber.CalculationError, leftOperand: NSDecimalNumber, rightOperand: NSDecimalNumber?) -> NSDecimalNumber? {
        //very bad, needs to some exception handling
        return nil
    }
        
    func round(value: String, style: RoundStyle) -> NSDecimalNumber? {
        var decimal = NSDecimalNumber(0)
        let temp = Double(value) ?? 0
        
        switch style{
        case .decades:
            let temp1 = temp * 0.1
            decimal = NSDecimalNumber(floatLiteral: temp1)
        case .hundreds:
            let temp2 = temp * 0.01
            decimal = NSDecimalNumber(floatLiteral: temp2)
        }
        let tempResult = decimal.rounding(accordingToBehavior: self)
        switch style {
        case .decades:
            return (tempResult as Decimal * 10) as NSDecimalNumber
        case .hundreds:
            return (tempResult as Decimal * 100) as NSDecimalNumber
        }
    }
    
    enum RoundStyle {
        case hundreds
        case decades
    }
}