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。但是当我实际上运行我的应用程序并输入一个数量来计算（例如 23.45）时，它会出现超过 2 位小数。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

如果你想强制货币为 $，你可以使用这个字符串初始值设定项：

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

如果你想让它完全依赖于设备的语言环境设置，你应该使用NumberFormatter。这将考虑货币的小数位数以及正确定位货币符号。例如。双精度值 2.4 将 return es_ES 区域设置为“2,40 €”，jp_JP 区域设置为“¥ 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

最好的方法是创建一个 NSNumberFormatter。（NumberFormatter in Swift 3.）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。

作为使用 NumberFormatter 的替代方法，如果您想强制使用美国格式的美元和美分字符串，您可以按以下方式格式化：

let amount: Double = 123.45

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

Answer 3

方法如下：

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

第 1 行：您正在获取当前语言环境

第 2 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 截断为小数点后两位。

Answer 4

除了别人讨论的NumberFormatter或者String(format:)，你可以考虑使用Decimal或者NSDecimalNumber，自己控制四舍五入，避免浮动点问题。如果您正在做一个简单的小费计算器，那可能没有必要。但是，如果您要在一天结束时将小费相加，如果您不对数字进行四舍五入 and/or 使用十进制数进行计算，则可能会引入错误。

所以，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：

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)")

在哪里

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，您可以将上述所有“2 位小数”引用替换为适合您使用的货币的任何数字（或者可能使用小数位数的变量）。

Answer 5

你可以这样转换：这个函数转换为你保留 maximumFractionDigits，只要你想做

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 class 模型中创建它然后当你打电话时，你可以接受另一个 class ，就像这样

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

Answer 6

如何在 Swift 4:

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 ,999.99 in the US locale

Answer 7

您可以为字符串或 Int 创建一个扩展，我将展示一个使用 String

的示例

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 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 return 0.00！在我看来，访问它时 Extenstion Perfect return 0.00！为什么？

Answer 9

 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 10

这是我一直在做的一个简单方法。

extension String {
    func toCurrency(Amount: NSNumber) -> String {
        var currencyFormatter = NumberFormatter()
        currencyFormatter.usesGroupingSeparator = true
        currencyFormatter.numberStyle = .currency
        currencyFormatter.locale = Locale.current

        return currencyFormatter.string(from: Amount)!
    }
}

使用如下

let amountToCurrency = NSNumber(99.99)
String().toCurrency(Amount: amountToCurrency)

Answer 11

从 Swift 5.5 开始，您可以在 .formatted:

的帮助下完成此操作

import Foundation

let amount = 12345678.9
print(amount.formatted(.currency(code: "USD")))
// prints: ,345,678.90

这应该支持最常见的货币代码，例如“EUR”、“GBP”或“CNY”。

同样，您可以将区域设置附加到 .currency:

print(amount.formatted(
    .currency(code:"EUR").locale(Locale(identifier: "fr-FR"))
))
// prints: 12 345 678,90 €

Answer 12

2022 年使用 Swift 5.5，我创建了扩展程序，使用您设备的区域设置或您作为参数传递的区域设置将 Float 或 Double 转换为货币。你可以在这里查看 https://github.com/ahenqs/SwiftExtensions/blob/main/Currency.playground/Contents.swift

import UIKit

extension NSNumber {
    
    /// Converts an NSNumber into a formatted currency string, device's current Locale.
    var currency: String {
        return self.currency(for: Locale.current)
    }
    
    /// Converts an NSNumber into a formatted currency string, using Locale as a parameter.
    func currency(for locale: Locale) -> String {
        let numberFormatter = NumberFormatter()
        numberFormatter.usesGroupingSeparator = locale.groupingSeparator != nil
        numberFormatter.numberStyle = .currency
        numberFormatter.locale = locale
        
        return numberFormatter.string(from: self)!
    }
}

extension Double {
    
    /// Converts a Double into a formatted currency string, device's current Locale.
    var currency: String {
        return NSNumber(value: self).currency(for: Locale.current)
    }
    
    /// Converts a Double into a formatted currency string, using Locale as a parameter.
    func currency(for locale: Locale) -> String {
        return NSNumber(value: self).currency(for: locale)
    }
}

extension Float {
    
    /// Converts a Float into a formatted currency string, device's current Locale.
    var currency: String {
        return NSNumber(value: self).currency(for: Locale.current)
    }
    
    /// Converts a Float into a formatted currency string, using Locale as a parameter.
    func currency(for locale: Locale) -> String {
        return NSNumber(value: self).currency(for: locale)
    }
}

let amount = 3927.75 // Can be either Double or Float, since we have both extensions.
let usLocale = Locale(identifier: "en-US") // US
let brLocale = Locale(identifier: "pt-BR") // Brazil
let frLocale = Locale(identifier: "fr-FR") // France
print("\(Locale.current.identifier) -> " + amount.currency) // default current device's Locale.
print("\(usLocale.identifier) -> " + amount.currency(for: usLocale))
print("\(brLocale.identifier) -> " + amount.currency(for: brLocale))
print("\(frLocale.identifier) -> " + amount.currency(for: frLocale))

// will print something like this:
// en_US -> ,927.75
// en-US -> ,927.75
// pt-BR -> R$ 3.927,75
// fr-FR -> 3 927,75 €

希望对您有所帮助，编码愉快！

如何将 Double 格式化为货币 - Swift 3

How to format a Double into Currency - Swift 3

formatting

currency

ios

swift