如何将 Double 格式化为货币 - Swift 3 [英] How to format a Double into Currency - Swift 3

问题描述

我是 Swift 编程新手，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.但是当我实际运行我的应用程序并输入一个要计算的数量(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?

I'm new to Swift programming and I've been creating a simple tip calculator app in Xcode 8.2, I have my calculations set up within my IBAction below. But when I actually run my app and input an amount to calculate (such as 23.45), it comes up with more than 2 decimal places. How do I format it to .currency in this case?

@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)"
    }
}

推荐答案

如果你想强制货币为$，你可以使用这个字符串初始化器:

You can use this string initializer if you want to force the currency to $:

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

如果您希望它完全依赖于设备的区域设置，您应该使用 NumberFormatter.这将考虑货币的小数位数以及正确定位货币符号.例如.对于 es_ES 语言环境，双精度值 2.4 将返回2,40€"，对于 jp_JP 语言环境返回¥ 2".

If you want it to be fully dependent on the locale settings of the device, you should use a NumberFormatter. This will take into account the number of decimal places for the currency as well as positioning the currency symbol correctly. E.g. the double value 2.4 will return "2,40 €" for the es_ES locale and "¥ 2" for the jp_JP locale.

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)"
}

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