從字符串中提取貨幣

Question

這是Swift 2.1。

你將如何去提取一個字符串，看起來像「添加蛋（£2.00）」的金額？在這個例子中，我需要「2.00」部分。

難道要檢查括號內的任何內容嗎？還是有更有效的方法呢？即正則表達式或什麼？

Answer 1

有很多方法可以實現你想要的東西 - 這裏有一個簡單的例子，用正則表達式。

我使用(?<=\\()[^\\)]+找到(和)之間的任何東西，然後我用了幾個範圍，以提取值：一個是貨幣符號，另一個用於值。

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後安全地解開該可選的結果：

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：

貨幣是 '£' 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) 

//這將打印2.00

Answer 3

'純'快速解決方案，無需支架

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號，沒有問題......

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] 
*/