设置大货币数字的格式

使用 FormatStyle API，是否可以使用“20M”或“10k”等尾随 SI 单位来格式化大数字？特别是，我正在寻找一种使用适当的本地化和货币符号来格式化大货币值（例如“$20M”）的方法。

我目前有一个货币格式化程序：

extension FormatStyle where Self == FloatingPointFormatStyle<Double>.Currency {
    public static var dollars: FloatingPointFormatStyle<Double>.Currency {
        .currency(code: "usd").precision(.significantDigits(2))
    }
}

我想将其扩展为格式Double(20_000_000)为“2000万美元”。

您可以创建一个自定义struct符合FormatStyle

public struct ShortCurrency<Value>: FormatStyle, Equatable, Hashable, Codable where Value :  BinaryFloatingPoint{
    let locale: Locale
    enum Options: Int{
        case million = 2
        case billion = 3
        case trillion = 4
        
        func short(locale: Locale) -> String{
            switch self {
            case .million:
                return millionAbbr[locale, default: "M"]
            case .billion:
                return billionAbbr[locale, default: "B"]
            case .trillion:
                return trillionAbbr[locale, default: "T"]
            }
        }
        ///Add other supported locales
        var millionAbbr: [Locale: String] { [Locale(identifier: "en_US") : "M"]}
        var billionAbbr: [Locale: String]  { [Locale(identifier: "en_US") : "B"]}
        var trillionAbbr: [Locale: String]  { [Locale(identifier: "en_US") : "T"]}
    }
    public func format(_ value: Value) -> String {
        let f = NumberFormatter()
        f.locale = locale
        f.numberStyle = .currency
        f.usesSignificantDigits = true

        let basic = f.string(for: value) ?? "0"
        let count = basic.count(of: ".000")
        //Checks for million value
        if let abbr = Options(rawValue: count)?.short(locale: f.locale){
            //Get the symbol and the most significant numbers
            var short = String(basic.prefix(basic.count - (4*count)))
            //Append from the dictionary based on locale
            short.append(abbr)
            //return modified string
            return short
        }else{
            //return the basic string
            return basic
        }
    }
    
}

extension String {
    
    func count(of string: String) -> Int {
        guard !string.isEmpty else{
            return 0
        }
        var count = 0
        var searchRange: Range<String.Index>?
        
        while let foundRange = range(of: string, options: .regularExpression, range: searchRange) {
            count += 1
            searchRange = Range(uncheckedBounds: (lower: foundRange.upperBound, upper: endIndex))
        }
        return count
    }
}

然后延伸FormatStyle

@available(iOS 15.0, *)
extension FormatStyle where Self == FloatingPointFormatStyle<Double>.Currency {
    public static func shortCurrency (locale: Locale? = nil) -> ShortCurrency<Double> {
        return ShortCurrency(locale: locale ?? .current)
    }
}

它将像任何其他产品一样可供使用FormatStyle

Text(Double(20_000_000), format: .shortCurrency())