swift - 货币模式下小负数的 NumberFormatter 不正确行为

Question

当使用 NumberFormatter 并将 numberStyle 设置为 .currency 时，格式化程序会按预期将所有数字四舍五入到小数点后两位。但是，对于小负数，其值四舍五入到小数点后 2 位为 0(数字 >= -0.005)，输出字符串包含负号，因此变为 -$0.00 而不是 $0.00.

是否可以通过切换 NumberFormatter 的某些属性来改变这种行为，而不必使用变通方法？目前，我自己将值四舍五入到小数点后两位，检查输出是否为 -0 并采取相应措施。但是，如果 NumberFormatter 可以设置为不区分 -0 和 0，那就太好了。

下面的代码显示了问题和我当前的解决方法(随意在 Playground 上测试)- 我知道 Locale 应该根据 currencySymbol 设置，但是这只是展示问题的代码，不是生产代码):

public class CurrencyFormatter {

    private let formatter: NumberFormatter

    public init(locale: Locale = Locale.current) {
        let formatter = NumberFormatter()
        formatter.locale = locale
        formatter.numberStyle = .currency
        self.formatter = formatter
    }

    // Adds currency symbol and returns a string e.g. input 1 output "£1"
    public func formatWithCurrencySymbol(value: Decimal, currencyCode: String) -> String? {
        formatter.currencyCode = currencyCode

        // Workaround for cases when the currency behaviour rounds small negative values (<0.0051) to -0.00, where we don't want to have a - sign
        var value = value
        if value < 0 {
            let roundedValue = round(Double(truncating: value as NSDecimalNumber) * 100.0)
            if roundedValue == 0 && roundedValue.sign == .minus {
                value = 0
            }
        }

        return formatter.string(for: value)
    }

    public func formatWithCurrencySymbolNoWorkaround(value: Decimal, currencyCode: String) -> String? {
        formatter.currencyCode = currencyCode
        return formatter.string(for: value)
    }
}

let formatter = CurrencyFormatter()

formatter.formatWithCurrencySymbol(value: 0.01, currencyCode: "USD") // "$0.01"
formatter.formatWithCurrencySymbol(value: -0.001, currencyCode: "EUR") // "€0.00"
formatter.formatWithCurrencySymbol(value: -0.0002, currencyCode: "EUR") // "€0.00"
formatter.formatWithCurrencySymbol(value: -0.01, currencyCode: "EUR") // "-€0.01"

formatter.formatWithCurrencySymbol(value: 0.01, currencyCode: "USD") // "$0.01"
formatter.formatWithCurrencySymbol(value: -0.001, currencyCode: "EUR") // "-€0.00"
formatter.formatWithCurrencySymbol(value: -0.0002, currencyCode: "EUR") // "-€0.00"
formatter.formatWithCurrencySymbol(value: -0.01, currencyCode: "EUR") // "-€0.01"
formatter.formatWithCurrencySymbolNoWorkaround(value: -0.005, currencyCode: "EUR") // "-€0.00"

Answer 1

您可以添加简单的逻辑来检查该值是否小于 -0.01，如果是，则返回绝对值。

return value < -0.01 ? formatter.string(for: abs(value)) : formatter.string(for: value)