Parse string with currency symbol and value-CodePudding

I am trying to parse a list of input strings from an Excel file that can have a 'currency' value, and it could be in any currency. For e.g.

$200
£300
€200
CA$300

What's the best way to parse out the currency symbol and the numeric value? I'm trying to do this with a NumberFormatter but it doesn't work for the 'euro' or the 'CAD' value.

Here is my code:

let currencyFormatter = NumberFormatter()
currencyFormatter.numberStyle = .currency
currencyFormatter.maximumFractionDigits = 2

let trimmedString = String(currencyString.filter { String($0).rangeOfCharacter(from: CharacterSet(charactersIn: "0123456789.,")) == nil }).trimmingCharacters(in: .whitespacesAndNewlines)

if trimmedString.count > 0 && Locale.current.currencySymbol != trimmedString {
    // Currency symbol is *not* local currency, so lookup the locale for it
    let allLocales = Locale.availableIdentifiers.map({Locale(identifier: $0)})
    if let localeForSymbol = allLocales.filter({$0.currencySymbol == trimmedString}).first {
        currencyFormatter.locale = localeForSymbol
    }
}

if let numberValue = currencyFormatter.number(from: currencyString) {
    print ("\(NSDecimalNumber(decimal: numberValue.decimalValue))")
}

What am I getting wrong here? Or is this not possible without using some regex expressions?

CodePudding user response：

you could try this "...to parse out the currency symbol and the numeric value":

let currencyString = "CA$300"

let valueString = currencyString.filter {
    CharacterSet(charactersIn: "0123456789.,").isSuperset(of: CharacterSet(charactersIn: String($0)))
}.trimmingCharacters(in: .whitespacesAndNewlines)
print("---> valueString: \(valueString) ")

let symbol = currencyString.replacingOccurrences(of: valueString, with: "")
print("---> symbol: \(symbol)")

CodePudding user response：

@workingdog has a valid answer. An alternative, and one I always reach for, is to use regex, where 3 simple regex can be used to identify any non-numeric leading characters, the numeric characters, and any non-numeric postfix characters:

let prefixRegex = #"^[^0-9] "#
let numRegex = #"[0-9] "#
let postfixRegex = #"[^0-9] $"#

These can then be used with String's .range(of: options:) using the .regularExpression option to get the element's range, and then use that to extract the relevant SubString.

As a very quick demo of this in action:

["$20", "£300", "€200", "CA$300", "798xyz", "$123abc"]
   .forEach{string in
      var components: [Range<String.Index>?] = []
      
      components.append( string.range(of: prefixRegex, options: .regularExpression))
      components.append( string.range(of: numRegex, options: .regularExpression))
      components.append( string.range(of: postfixRegex, options: .regularExpression))
      
      print(components
         .map{ $0 != nil ? String(string[$0!]).padded(to: 8) : String(repeating: " ", count: 8) }
         .joined(separator: "")
      )
   }

This provides an output of

$       20              
£       300             
€       200             
CA$     300             
        798     xyz     
$       123     abc

NB: .padded(to:) is a utility method that pads a string to a specified length with spaces.

CodePudding user response：

You can find the index of the first digit in the string and then extract the number (and currency) using that index.

Here is one way that extracts a tuple of currency and amount

let values = ["$200", "£300", "€200", "CA$300"]

var amounts = [(String, Double)]()
for value in values {
    if let index = value.firstIndex(where: \.isNumber) {
        let currency = String(value.prefix(upTo: index))
        guard let amount = Double(String(value.suffix(from: index))) else {
            break
        }
        amounts.append((currency, amount))
    }
}

Result:

[("$", 200.0), ("£", 300.0), ("€", 200.0), ("CA$", 300.0)]