Swift：如何限制浮点数中的小数点？

Question

我的问题是我如何得到我的＆＃34;计算＆＃34;和＆＃34;计算总数＆＃34;变量将结果显示为仅两位小数？

@IBOutlet weak var calculateLabel: UILabel!

@IBOutlet weak var calculateTotalLabel: UILabel!

@IBAction func calculateButton(sender: UIButton) {



    var calculated = correctNumber / (correctNumber + incorrectNumber) * 100
    calculateLabel.text = ("\(calculated)% without cues.")



    var calculatedTotal = correctNumber / (correctNumber + incorrectNumber + verbalNumber + visualNumber + tactileNumber) * 100
           calculateTotalLabel.text = "\(calculatedTotal)% without cues."


}

Answer 1

您可以在Swift中使用类似C的格式说明符，如下所示：

println(String(format: "%.2f", myFloat))

或

calculatedTotal.text = String(format: "%.2f", myFloat)

Answer 2

为最终用户格式化数字时，我建议使用NSNumberFormatter，以尊重用户当前的NSLocale。例如，要将这些数字格式化为两位小数，您可能会执行以下操作：

@IBAction func calculateButton(sender: UIButton) {
    let formatter = NSNumberFormatter()
    formatter.minimumFractionDigits = 2
    formatter.maximumFractionDigits = 2

    let calculated = correctNumber / (correctNumber + incorrectNumber) * 100.0
    calculateLabel.text = ("\(formatter.stringFromNumber(calculated)!)% without cues.")

    let calculatedTotal = correctNumber / (correctNumber + incorrectNumber + verbalNumber + visualNumber + tactileNumber) * 100.0
    calculateTotalLabel.text = "\(formatter.stringFromNumber(calculatedTotal)!)% without cues."
}