Question

我正在尝试对文本字段进行一些计算，我使用双打来实现它：

let firstValue = Double(miles.text!)
    let secondValue = Double(payPerMile.text!)
    let formatter = NumberFormatter()
    formatter.numberStyle = .currency
    formatter.minimumFractionDigits = 2
    formatter.maximumFractionDigits = 2
    formatter.locale = Locale.current
    formatter.usesGroupingSeparator = true

    let result = Double(firstValue! * secondValue!) as NSNumber
    grossPay.text = "\(formatter.string(from: result)!)"

在对该主题进行更多研究时，我被告知使用双打并不是最佳选择，所以我尝试使用NSDecimalNumber。

我的问题是我无法弄清楚如何在切换时让它工作。

@IBAction func miles(_ sender: Any) {

    let firstValue = NSDecimalNumber(string: miles.text)
    let formatter = NumberFormatter()
    formatter.numberStyle = .decimal
    formatter.maximumFractionDigits = 2
    formatter.usesGroupingSeparator = true

    miles.text = "\(formatter.string(from: firstValue as NSNumber)!)"

}

@IBAction func payPerMile(_ sender: Any) {

    let firstValue = NSDecimalNumber(string: payPerMile.text)
    let formatter = NumberFormatter()
    formatter.numberStyle = .currency
    formatter.minimumFractionDigits = 2
    formatter.maximumFractionDigits = 2
    formatter.locale = Locale.current
    formatter.usesGroupingSeparator = true

    payPerMile.text = "\(formatter.string(from: firstValue as NSNumber)!)"

}

@IBAction func grossPay(_ sender: Any) {

    let firstValue = NSDecimalNumber(string: miles.text!)
    let secondValue = NSDecimalNumber(string: payPerMile.text!)
    let formatter = NumberFormatter()
    formatter.numberStyle = .currency
    formatter.minimumFractionDigits = 2
    formatter.maximumFractionDigits = 2
    formatter.locale = Locale.current
    formatter.usesGroupingSeparator = true

    let result = (firstValue as Decimal) * (secondValue as Decimal) as NSDecimalNumber
    grossPay.text = "\(formatter.string(from: result)!)"

只是给我NaN的结果

miles.text格式化为.decimal payPerMile.text格式化为.currency

我不确定这是不是我问题的一部分。

Answer 1

如果payPerMile的格式为.currency，那么它可能包含货币字符。您不能简单地从这样的字符串创建NSDecimalNumber。

您的第二行为NaN提供secondValue。

您可以使用NumberFormatter从字符串中获取NSNumber。

let formatter = NumberFormatter()
formatter.numberStyle = .currency
let payPerMileNumber = formatter.number(from: "$34.75") // NSNumber with 34.75

NSDecimal数字乘法

1 个答案: