如何实现 NumberFormatter

Question

我想让我的计数器只显示小数点后八位。最后一位数字一旦变为 0 就会消失。试图让尾随零显示自己。

有人告诉我使用 NumberFormatter。我如何获得它以便 secondUpdateLabel 继承格式化程序？

var secondTimer = Timer()
var secondCounter: Double = 70.000000
var secondDecreaser: Double = 0.000001


func secondStartCounting(initialNumber x: Double, decreaseBy y: Double) {
    self.secondCounter = x
    self.secondDecreaser = y

    self.secondTimer.invalidate()

    let secondTimer = Timer(timeInterval: 0.38, target: self, selector: #selector(ViewController.secondUpdateTimer), userInfo: nil, repeats: true)

    RunLoop.main.add(secondTimer, forMode: .commonModes)
    self.secondTimer = secondTimer


}


@objc func secondUpdateTimer() {
    secondCounter -= secondDecreaser

    let secondUpdateLabel = secondCounter

    let formatter = NumberFormatter()
    formatter.numberStyle = NumberFormatter.Style.decimal
    formatter.usesSignificantDigits = true
    formatter.minimumFractionDigits = 8
    formatter.maximumFractionDigits = 8

    // not proper code next. just want to know how to get secondUpdateLabel to inherit the properties I applied to formatter. not sure what the next steps are 
    secondStat.text = 


}

Answer 1

这对我有用！

var secondTimer = Timer()
var secondCounter: Double = 70.000000
var secondDecreaser: Double = 0.000001


func secondStartCounting(initialNumber x: Double, decreaseBy y: Double) {
    self.secondCounter = x
    self.secondDecreaser = y

    self.secondTimer.invalidate()

    let secondTimer = Timer(timeInterval: 0.0000001, target: self, selector: #selector(ViewController.secondUpdateTimer), userInfo: nil, repeats: true)

    RunLoop.main.add(secondTimer, forMode: .commonModes)
    self.secondTimer = secondTimer


}


@objc func secondUpdateTimer() {
    secondCounter -= secondDecreaser

    let secondUpdateLabel = secondCounter

    let formatter = NumberFormatter()
    formatter.numberStyle = NumberFormatter.Style.decimal
    formatter.usesSignificantDigits = false
    formatter.minimumFractionDigits = 8
    formatter.maximumFractionDigits = 8

    secondStat.text = formatter.string(from: NSNumber(value: secondUpdateLabel))


}

发现我必须将 usesSignificantDigits 设置为 false，我实现的最后一行代码解决了我的问题。

如何实现 NumberFormatter

How to implement NumberFormatter

swift

nsnumberformatter