从字符串中提取货币

Question

这是Swift 2.1。

你将如何去提取一个字符串，看起来像“添加蛋（£2.00）”的金额？在这个例子中，我需要“2.00”部分。

难道要检查括号内的任何内容吗？还是有更有效的方法呢？即正则表达式或什么？

Answer 1

有很多方法可以实现你想要的东西 - 这里有一个简单的例子，用正则表达式。

我使用(?<=\\()[^\\)]+找到(和)之间的任何东西，然后我用了几个范围，以提取值：一个是货币符号，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) 
    } 
} 

呼叫上的字符串的方法然后安全地解开该可选的结果：

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：

货币是 '£' 和值是 '2.00'

Answer 2

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

//这将打印2.00

Answer 3

'纯'快速解决方案，无需支架

let str = ["add egg £ 2.00", 
      "the price is $12.00 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($0, currency: "£$€") } 
print(values) 
/* 
[2.0, 12.0, 10.220000000000001, nan] 
*/ 

如果你真的需要有括号，没有问题......

let str = ["add egg (£2.00)", 
      "the price is ($12.00) per unit", 
      "send (€10.22) to somebody", 
      "invalid ($-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($0, currency: "£$€") } 
print(values) 
/* 
[2.0, 12.0, 10.220000000000001, -12.0] 
*/