Question

我是Swift编程的新手，我在Xcode 8.2中创建了一个简单的小费计算器应用程序，我在下面的IBAction中设置了我的计算。但是当我实际运行我的应用并输入要计算的金额（例如23.45）时，它会出现超过2个小数位。在这种情况下，如何将其格式化为.currency？

@IBAction func calculateButtonTapped(_ sender: Any) {

    var tipPercentage: Double {

        if tipAmountSegmentedControl.selectedSegmentIndex == 0 {
            return 0.05
        } else if tipAmountSegmentedControl.selectedSegmentIndex == 1 {
            return 0.10
        } else {
            return 0.2
        }
    }

    let billAmount: Double? = Double(userInputTextField.text!)

    if let billAmount = billAmount {
        let tipAmount = billAmount * tipPercentage
        let totalBillAmount = billAmount + tipAmount

        tipAmountLabel.text = "Tip Amount: $\(tipAmount)"
        totalBillAmountLabel.text = "Total Bill Amount: $\(totalBillAmount)"
    }
}

Answer 1

如果要强制货币为$：

，可以使用此字符串初始值设定项

String(format: "Tip Amount: $%.02f", tipAmount)

如果您希望它完全依赖于设备的区域设置，则应使用NumberFormatter。这将考虑货币的小数位数以及正确定位货币符号。例如。对于es_ES语言环境，double值2.4将返回“2,40€”，对于jp_JP语言环境将返回“¥2”。

let formatter = NumberFormatter()
formatter.locale = Locale.current // Change this to another locale if you want to force a specific locale, otherwise this is redundant as the current locale is the default already
formatter.numberStyle = .currency
if let formattedTipAmount = formatter.string(from: tipAmount as NSNumber) {
    tipAmountLabel.text = "Tip Amount: \(formattedTipAmount)"
}

Answer 2

执行此操作的最佳方法是创建NSNumberFormatter。（Swift 3中的NumberFormatter。）您可以请求货币，它会设置字符串以遵循用户的本地化设置，这很有用。

如果你想强制使用美国格式的美元和美分字符串，你可以这样格式化：

let amount: Double = 123.45

let amountString = String(format: "$%.02f", amount)

Answer 3

除了其他人讨论的NumberFormatter或String(format:)之外，您可能还需要考虑使用Decimal或NSDecimalNumber并自行控制舍入，从而避免出现浮点问题。如果你正在做一个简单的小费计算器，那可能就没有必要了。但是，如果您在一天结束时添加提示，如果您不对数字进行舍入和/或使用十进制数进行数学运算，则可能会引入错误。

因此，请继续配置格式化程序：

let formatter: NumberFormatter = {
    let _formatter = NumberFormatter()
    _formatter.numberStyle = .decimal
    _formatter.minimumFractionDigits = 2
    _formatter.maximumFractionDigits = 2
    _formatter.generatesDecimalNumbers = true
    return _formatter
}()

然后，使用十进制数字：

let string = "2.03"
let tipRate = Decimal(sign: .plus, exponent: -3, significand: 125) // 12.5%
guard let billAmount = formatter.number(from: string) as? Decimal else { return }
let tip = (billAmount * tipRate).rounded(2)

guard let output = formatter.string(from: tip as NSDecimalNumber) else { return }
print("\(output)")

其中

extension Decimal {

    /// Round `Decimal` number to certain number of decimal places.
    ///
    /// - Parameters:
    ///   - scale: How many decimal places.
    ///   - roundingMode: How should number be rounded. Defaults to `.plain`.
    /// - Returns: The new rounded number.

    func rounded(_ scale: Int, roundingMode: RoundingMode = .plain) -> Decimal {
        var value = self
        var result: Decimal = 0
        NSDecimalRound(&result, &value, scale, roundingMode)
        return result
    }
}

显然，您可以替换以上所有＆＃34; 2小数位＆＃34;任何数字的引用都适用于您正在使用的货币（或者可能使用变量作为小数位数）。

Answer 4

如何在Swift 4中做到这一点：

let myDouble = 9999.99
let currencyFormatter = NumberFormatter()
currencyFormatter.usesGroupingSeparator = true
currencyFormatter.numberStyle = .currency
// localize to your grouping and decimal separator
currencyFormatter.locale = Locale.current

// We'll force unwrap with the !, if you've got defined data you may need more error checking

let priceString = currencyFormatter.string(from: NSNumber(value: myDouble))!
print(priceString) // Displays $9,999.99 in the US locale

Answer 5

您可以为字符串或整数创建扩展名，我将使用字符串作为示例

extension String{
     func toCurrencyFormat() -> String {
        if let intValue = Int(self){
           let numberFormatter = NumberFormatter()
           numberFormatter.locale = Locale(identifier: "ig_NG")/* Using Nigeria's Naira here or you can use Locale.current to get current locale, please change to your locale, link below to get all locale identifier.*/ 
           numberFormatter.numberStyle = NumberFormatter.Style.currency
           return numberFormatter.string(from: NSNumber(value: intValue)) ?? ""
      }
    return ""
  }
}

link to get all locale identifier

Answer 6

您可以这样转换：只要您愿意，此func转换为您的maximumFractionDigits

static func df2so(_ price: Double) -> String{
        let numberFormatter = NumberFormatter()
        numberFormatter.groupingSeparator = ","
        numberFormatter.groupingSize = 3
        numberFormatter.usesGroupingSeparator = true
        numberFormatter.decimalSeparator = "."
        numberFormatter.numberStyle = .decimal
        numberFormatter.maximumFractionDigits = 2
        return numberFormatter.string(from: price as NSNumber)!
    }

我在类Model中创建它然后当你打电话时，你可以接受另一个类，比如这个

 print("InitData: result convert string " + Model.df2so(1008977.72))
//InitData: result convert string "1,008,977.72"

Answer 7

 extension String{
    func convertDoubleToCurrency() -> String{
        let amount1 = Double(self)
        let numberFormatter = NumberFormatter()
        numberFormatter.numberStyle = .currency
        numberFormatter.locale = Locale(identifier: "en_US")
        return numberFormatter.string(from: NSNumber(value: amount1!))!
    }
}

Answer 8

extension Float {
    var localeCurrency: String {
        let formatter = NumberFormatter()
        formatter.numberStyle = .currency
        formatter.locale = .current
        return formatter.string(from: self as NSNumber)!
    }
}
    amount = 200.02
    print("Amount Saved Value ",String(format:"%.2f", amountSaving. localeCurrency))

对我来说，它的回报是0.00！对我来说，扩展性完美访问它时返回0.00！为什么？

Answer 9

以下是：

    let currentLocale = Locale.current
    let currencySymbol = currentLocale.currencySymbol
    let outputString = "\(currencySymbol)\(String(format: "%.2f", totalBillAmount))"

第一行：您正在获取当前区域设置

第二行：您正在获取该语言环境的currencySymbol。（$，£等）

第3行：使用格式初始值设定项将Double到2的小数位截断。

如何将Double格式化为货币 - Swift 3

9 个答案: