从字符串中提取货币

Question

这是Swift 2.1.

如何从类似于 "add egg (£2.00)" 的字符串中提取金额？在这个例子中，我需要“2.00”部分。

查找括号中的内容会不会是一个硬检查？或者有更有效的方法吗？ IE。正则表达式之类的？

Answer 1

var myString = "add egg (£2.00)"
myString = myString.stringByReplacingOccurrencesOfString("", withString: "")
let components = myString.componentsSeparatedByString("add egg (£")
let finalString = components[1].stringByReplacingOccurrencesOfString(")", withString: "")
print(finalString)

//这会打印 2.00

Answer 2

有很多方法可以实现您想要的 - 这是一个使用正则表达式的简单示例。

我使用 (?<=\()[^\)]+ 来查找 ( 和 ) 之间的任何内容，然后我使用几个范围来提取值：一个用于货币符号，另一个用于值。

extension String {
    func extractValueBetweenParenthesis() -> (currency: String?, value: String?) {
        if let range = self.rangeOfString("(?<=\()[^\)]+", options: .RegularExpressionSearch) {
            let cr = range.startIndex..<range.startIndex.advancedBy(1)
            let vr = range.startIndex.advancedBy(1)..<range.endIndex
            return (currency: self.substringWithRange(cr), value: self.substringWithRange(vr))
        }
        return (nil, nil)
    }
}

对字符串调用该方法，然后安全地解包可选结果：

let str = "add egg (£2.00)"
let result = str.extractValueBetweenParenthesis()
if let currency = result.currency, value = result.value {
    print("Currency is '\(currency)' and value is '\(value)'")
}

打印：

Currency is '£' and value is '2.00'

Answer 3

'pure' Swift 解决方案，不需要括号

let str = ["add egg £ 2.00",
           "the price is .00 per unit",
           "send €10.22 to somebody",
           "invalid $(12)"]

func value(str: String, currency: String)->Double {
    var chars = str.characters
    let currs = currency.characters

    while !currs.contains(chars.popFirst() ?? " ") {}

    let arr = chars.split(" ")
    guard let value = arr.first,
        let d  = Double(String(value)) else { return Double.NaN }
    return d
}

let values = str.flatMap { value([=10=], currency: "£$€") }
print(values)
/*
 [2.0, 12.0, 10.220000000000001, nan]
 */

如果你真的需要括号，没问题...

let str = ["add egg (£2.00)",
           "the price is (.00) per unit",
           "send (€10.22) to somebody",
           "invalid ($-12)"]

func value(str: String, currency: String)->Double {
    var chars = str.characters
    let currs = currency.characters

    while !currs.contains(chars.popFirst() ?? " ") {}

    let arr = chars.split(")")
    guard let value = arr.first,
        let d  = Double(String(value)) else { return Double.NaN }
    return d
}

let values = str.flatMap { value([=11=], currency: "£$€") }
print(values)
/*
 [2.0, 12.0, 10.220000000000001, -12.0]
 */

从字符串中提取货币

Extracting currency from string

currency

substring

swift2