在Swift闭包中使用多个分隔符分割数字字符串? [英] can I split a numeric string using multiple separators in a Swift closure?

问题描述

我有一个包含小数和十进制数字的字符串数组.

    let stringArray = [ "0.0", "193.16", "5/4", "503.42", "696.58", "25/16", "1082.89", "2/1"]

每个数组元素都映射在一个闭包中，在该闭包中从字符串中提取数字.

    let values = stringArray.map { s -> Double in

两个小数(请参见先前的帖子)

    let splitStrings = s.characters.split(separator: "/").map(String.init).map({ Double($0) })

或十进制

    let splitStrings = s.characters.split(separator: ".").map(String.init).map({ Double($0) })

问题:在Swift中，有一种方法可以使用多个分隔符来拆分字符串，以便单个闭包可以返回小数或小数?

(继续关闭)

switch (token)) {
case "/"  :
        print( "fraction")

        let pathA = splitString[0]!/splitString[1]!
        return pathA

case "."  :
        print( "decimal")

        let upperSplit = splitString[0]!
        let lowerSplit = splitString[1]! * 0.1  // restore decimal point
        let pathB = upperSplit+lowerSplit
        return pathB
        }
}

解决方案

如果您打算从中创建浮点数 十进制表示或小数表示，那么就没有 需要在小数点处分割字符串.

您可以尝试使用Double(string)转换字符串， 如果失败，请在斜杠处将其拆分并转换分子 和分母:

func doubleFromDecimalOrFraction(s: String) -> Double? {
    // Try to convert from decimal representation:
    if let value = Double(s) {
        return value
    }
    // Try to convert from fractional format:
    if let range = s.range(of: "/"),
        let num = Double(s.substring(to: range.lowerBound)),
        let den = Double(s.substring(from: range.upperBound)) {
        return num/den
    }
    // Invalid format
    return nil
}

(代替返回nil来获取无效输入，您也可以 考虑到throw错误，中止执行 fatalError()，或返回一些默认值.)

然后可以在每个数组元素上应用此实用功能":

let strings = [ "0.0", "193.16", "5/4", "503.42", "696.58", "25/16", "1082.89", "2/1"]
let values = strings.flatMap(doubleFromDecimalOrFraction)

I have a string array with fractional numbers and decimal numbers.

    let stringArray = [ "0.0", "193.16", "5/4", "503.42", "696.58", "25/16", "1082.89", "2/1"]

Each array element is mapped in a closure where numbers are extracted from the string.

    let values = stringArray.map { s -> Double in

either fractional (see earlier post)

    let splitStrings = s.characters.split(separator: "/").map(String.init).map({ Double($0) })

or decimal

    let splitStrings = s.characters.split(separator: ".").map(String.init).map({ Double($0) })

Question: In Swift is there a way to split the string using more than one separator so a single closure can return fractional values or decimal values ?

(continuation of closure)

switch (token)) {
case "/"  :
        print( "fraction")

        let pathA = splitString[0]!/splitString[1]!
        return pathA

case "."  :
        print( "decimal")

        let upperSplit = splitString[0]!
        let lowerSplit = splitString[1]! * 0.1  // restore decimal point
        let pathB = upperSplit+lowerSplit
        return pathB
        }
}

解决方案

If your intention is to create floating point numbers from either a decimal representation or a fraction, then there is no need to split the string at the decimal point.

You can try to convert the string with Double(string), and if that fails, split it at the slash and convert numerator and denominator separately:

func doubleFromDecimalOrFraction(s: String) -> Double? {
    // Try to convert from decimal representation:
    if let value = Double(s) {
        return value
    }
    // Try to convert from fractional format:
    if let range = s.range(of: "/"),
        let num = Double(s.substring(to: range.lowerBound)),
        let den = Double(s.substring(from: range.upperBound)) {
        return num/den
    }
    // Invalid format
    return nil
}

(Instead of returning nil for invalid input you might also consider to throw an error, to abort the execution with fatalError(), or to return some default value.)

This "utility function" can then be applied each array element:

let strings = [ "0.0", "193.16", "5/4", "503.42", "696.58", "25/16", "1082.89", "2/1"]
let values = strings.flatMap(doubleFromDecimalOrFraction)

这篇关于在Swift闭包中使用多个分隔符分割数字字符串?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！