Question

我在格式化iOS Swift中的double变量时遇到了问题

我拥有的变量类似于0.7, -4.56, 34.6，但它们的格式应为00.70, -04.56, 34.60

解决这个问题的最佳方法是什么？

Answer 1

签出此

extension Double {
    func formatNumber(minimumIntegerDigits: Int, minimumFractionDigits: Int, maximumFractionDigits: Int=2) -> String {
        let numberFormatter = NumberFormatter()
        numberFormatter.numberStyle = .decimal
        numberFormatter.minimumIntegerDigits = minimumIntegerDigits
        numberFormatter.minimumFractionDigits = minimumFractionDigits
        numberFormatter.maximumFractionDigits = maximumFractionDigits

        return numberFormatter.string(for: self) ?? ""
    }
}

999.989.formatNumber(minimumIntegerDigits: 2, minimumFractionDigits: 2) // => 999.99
9.989.formatNumber(minimumIntegerDigits: 2, minimumFractionDigits: 2) // => 09.99

Answer 2

像这样使用NumberFormatter：

let number = 0.7

let numberFormatter = NumberFormatter()

numberFormatter.minimumIntegerDigits = 2

numberFormatter.maximumFractionDigits = 2
numberFormatter.minimumFractionDigits = 2

numberFormatter.string(for: number)

或者将其定义为函数：

func format(_ x: Double) -> String? {
    guard abs(x) < 100 else {
        print("The argument must have 2 integer digits at maximum")
        return nil
    }

    let numberFormatter = NumberFormatter()

    numberFormatter.maximumIntegerDigits = 2
    numberFormatter.minimumIntegerDigits = 2

    numberFormatter.maximumFractionDigits = 2
    numberFormatter.minimumFractionDigits = 2

    return numberFormatter.string(for: x)
}

format(-0.7)  //"-00.70"
format(120)   //nil , and prints "The argument must have 2 integer digits at maximum"

请记住，方法Formatter.string(for:)返回一个可选字符串。

@LeoDabus指出，为避免每次调用此函数时都创建一个新的Number Formatter，我们可以在NumberFormatter上定义一个静态属性：

extension NumberFormatter {
    static let formatter_2Int_2Frac: NumberFormatter = {
        let numberFormatter = NumberFormatter()
        numberFormatter.maximumIntegerDigits = 2
        numberFormatter.minimumIntegerDigits = 2

        numberFormatter.maximumFractionDigits = 2
        numberFormatter.minimumFractionDigits = 2
        return numberFormatter
    }()
}

因此，上面的函数将如下所示：

func format(_ x: Double) -> String? {
    guard abs(x) < 100 else {
        print("The argument must have 2 integer digits at maximum")
        return nil
    }
    return NumberFormatter.formatter_2Int_2Frac.string(for: x)
}

Answer 3

另一个选择

let f = NumberFormatter()

f.minimumFractionDigits = 2

f.minimumIntegerDigits = 2

let str = f.string(from:-4.6)

print(str) // -04.60

Answer 4

let numberFormatter = NumberFormatter()
numberFormatter.numberStyle = .decimal
numberFormatter.minimumIntegerDigits = 2
numberFormatter.minimumFractionDigits = 2

let formattedNumbers = [0.7, -4.56, 34.6].flatMap { number in
    return numberFormatter.string(for: number)
}
print(formattedNumbers) //prints ["00.70", "-04.56", "34.60"]

格式化双变量-Swift

4 个答案: