Extracting currency value from a formatted string in Swift - swift

Question

I have the following string, from which I want to remove the currency formatting and extract the numeric value for manipulation:
"Product Price":"\u00a3314.95",
I've tried using the following code:
let productvalue = model[indexPath.row].productPrice ?? ""
let prodval = productvalue.replacingOccurrences(of: "\u00a3", with: "")
let proqty = model[indexPath.row].quantity ?? ""
let totalprice = (Int(prodval)) * (Int(proqty))
However, when I run this code, I am getting the following response from an API:
Binary operator '*' cannot be applied to two 'Int?' operands

Answer 1

The problem is that the init methods you use returns an optional value so you need to include a value in case the conversion from String to Int returns nil like
let value = Int(someString) ?? 0
but in your case you are dealing with decimal values so you need to convert to Double
let totalprice = (Double(prodval) ?? 0.0) * (Double(proqty) ?? 0.0)

Answer 2

You can use this extension that will help you remove currency symbols from the amount.
Replace your desired currency with $ for example use € instead of unicode.
extension String {
func removeFormatAmount() -> Double {
let formatter = NumberFormatter()
formatter.locale = Locale(identifier: "en_US")
formatter.numberStyle = .currency
formatter.currencySymbol = "$"
formatter.decimalSeparator = ","
return formatter.number(from: self) as Double? ?? 0
}
}
How to use this extension.
let currencyString = "$1,000.00"
let amount = currencyString.removeFormatAmount() // 1000.0

Answer 3

You can convert currency string to decimal
let str = "£300"
let formatter = NumberFormatter()
formatter.numberStyle = .currency
formatter.currencyCode = "GBP"
if let number = formatter.number(from: str) {
let amount = number.decimalValue
print(amount)
}

Answer 4

If you look closely the constructors of integers from string return optional values. So what you have is:
let totalprice = {
let a: Int? = Int(prodval)
let b: Int? = Int(proqty)
return a*b // Error
}()
a quick fix is to force-unwrap it using ! resulting in let totalprice = (Int(prodval))! * (Int(proqty))! but I would not suggest it because it may crash your app.
A but more elegant solution is to use defaults:
let totalprice = {
let a: Int = Int(prodval) ?? 0
let b: Int = Int(proqty) ?? 0
return a*b
}()
But on the other hand why are you even using integers here? What if the price is not a whole number? I suggest you rather use decimal numbers to handle these cases:
let a = NSDecimalNumber(string: prodval)
let b = NSDecimalNumber(string: proqty)
let totalprice = a.multiplying(by: b)
This is now working with decimal numbers directly. To get a double value or integer value you would simply need to use it's properties totalprice.doubleValue or totalprice.intValue. But there is no need for that either. If you need to convert it back to string simply use formatters:
let formatter = NumberFormatter()
formatter.numberStyle = .currency
formatter.currencySymbol = "$"
let finalOutput: String = formatter.string(from: totalprice)
There are many possible solutions to this and if possible I would try to do it all with formatters and decimal numbers. For instance in your case something like the following might do the trick:
private func generateFormatter(currencySymbol: String = "$", decimalSeparator: String = ".") -> NumberFormatter {
let formatter = NumberFormatter()
formatter.currencySymbol = currencySymbol
formatter.decimalSeparator = decimalSeparator
formatter.numberStyle = .currency
return formatter
}
private func parseValue(_ input: String?, formatterInfo: (currencySymbol: String, decimalSeparator: String)) -> NSNumber? {
guard let input = input else { return nil }
let formatter = generateFormatter(currencySymbol: formatterInfo.currencySymbol, decimalSeparator: formatterInfo.decimalSeparator)
return formatter.number(from: input)
}
private func multiplyValues(_ values: [String?], formatterInfo: (currencySymbol: String, decimalSeparator: String)) throws -> NSNumber {
return try values.reduce(NSDecimalNumber(value: 1.0)) { result, value in
guard let parsedValue = parseValue(value, formatterInfo: formatterInfo) else {
throw NSError(domain: "Parsing values", code: 400, userInfo: ["dev_message": "Could not parse a value \(value ?? "[Null value]")"])
}
return NSDecimalNumber(decimal: result.decimalValue).multiplying(by: NSDecimalNumber(decimal: parsedValue.decimalValue))
}
}
let values = ["$1.2", "$1.6", "$2"]
let result = try? multiplyValues(values, formatterInfo: ("$", "."))
let parsedResult: String = {
guard let result = try? multiplyValues(values, formatterInfo: ("$", ".")) else { return "Could not produce result" }
return generateFormatter(currencySymbol: "$", decimalSeparator: ".").string(from: result) ?? "Could not format result"
}()
print(result ?? "No result")
print(parsedResult)
I hope the code speaks for itself and you can see it is easy to change/inject different formats/symbols.