如何将Double格式化为货币 - Swift 3

Question

我是Swift编程的新手,我一直在Xcode 8.2中创建一个简单的tip计算器应用程序,我的计算设置在我的IBAction下面.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..currency在这种情况下如何格式化？

@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$,则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a 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

从 Swift 5.5 开始，您可以借助以下工具来完成此操作.formatted：

\n

import Foundation\n\nlet amount = 12345678.9\nprint(amount.formatted(.currency(code: "USD")))\n// prints: $12,345,678.90\n

\n

这应该支持最常见的货币代码，例如“EUR”、“GBP”或“CNY”。

\n

同样，您可以将区域设置附加到.currency：

\n

print(amount.formatted(\n    .currency(code:"EUR").locale(Locale(identifier: "fr-FR"))\n))\n// prints: 12\xe2\x80\xaf345\xe2\x80\xaf678,90\xc2\xa0\xe2\x82\xac\n

\n

Answer 3

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 4

最好的方法是创建一个NSNumberFormatter.(NumberFormatter在Swift 3中.)您可以请求货币,它将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 5

除了其他人讨论NumberFormatter或String(format:)讨论之外,您可能还想考虑使用Decimal或NSDecimalNumber控制自己的舍入,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.但是如果你正在做一些事情,比如在一天结束时添加提示,如果你没有对数字进行舍入和/或使用十进制数进行数学计算,则可能会引入错误.

所以,继续配置你的格式化程序:

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)")

哪里

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,您可以使用适合您正在使用的货币的任何数字替换所有上述"2位小数"引用(或者可能使用变量作为小数位数).

Answer 6

你可以为字符串或Int创建一个扩展,我会用String显示一个例子

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 ""
  }
}

链接以获取所有区域设置标识符

Answer 7

您可以像这样进行转换：此func转换可随时为您保留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Model类中创建它，然后在调用时可以接受另一个类，例如

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