Second decimal place gets truncated if it is 0 - swift

Question

I'm new to Swift, so bear with me. :)
I'm having trouble showing the output currency to two decimal places. Currently, it only shows one decimal place. For example, if I input $1.10, the output is $1.1.
However, if I input $1.11, the output is still $1.11.
func currencyInputDoubling() -> String {
var number: NSNumber!
let formatter = NumberFormatter()
formatter.numberStyle = .currencyAccounting
formatter.currencySymbol = CurrencyManager.shared.currentCurrency.sign
formatter.maximumFractionDigits = 2
formatter.minimumFractionDigits = 2
var amountWithPrefix = self
// remove from String: "$", ".", ","
let regex = try! NSRegularExpression(pattern: "[^0-9]", options: .caseInsensitive)
amountWithPrefix = regex.stringByReplacingMatches(in: amountWithPrefix, options: NSRegularExpression.MatchingOptions(rawValue: 0), range: NSMakeRange(0, self.count), withTemplate: "")
let double = (amountWithPrefix as NSString).doubleValue
number = NSNumber(value: (double / 100))
// if first number is 0 or all numbers were deleted
guard number != 0 as NSNumber else {
return ""
}
return "\(double / 100)"
}

Answer 1

I would suggest using Locale instead of currencySymbol and to create static number formatters that can be reused.
let currencyFormatter: NumberFormatter = {
let formatter = NumberFormatter()
formatter.numberStyle = .currency
formatter.locale = .current
return formatter
}()
let numberFormatter: NumberFormatter = {
let formatter = NumberFormatter()
formatter.numberStyle = .decimal
formatter.locale = .current
formatter.minimumFractionDigits = 2
formatter.maximumFractionDigits = 2
return formatter
}()
And then the method can be simplified as
func currencyInputDoubling(_ amountWithPrefix: String) -> String {
guard let value = currencyFormatter.number(from: amountWithPrefix) else { return "" }
return numberFormatter.string(from: value) ?? ""
}
If you need to set Locale to something else than .current you could pass it as an argument
func currencyInputDoubling(_ amountWithPrefix: String, using locale: Locale) -> String {
currencyFormatter.locale = locale
numberFormatter.locale = locale
guard let value = currencyFormatter.number(from: amountWithPrefix) else { return "" }
return numberFormatter.string(from: value) ?? ""
}

Answer 2

I would suggest, at a minimum, using the formatter you created, rather than doing string interpolation. When you return "\(double / 100)", using simple string interpolation, that can’t avail itself of the formatter’s fractional digits setting.
Perhaps:
func currencyInputDoubling() -> String {
let formatter = NumberFormatter()
formatter.numberStyle = .currencyAccounting
formatter.currencySymbol = CurrencyManager.shared.currentCurrency.sign
formatter.maximumFractionDigits = 2
formatter.minimumFractionDigits = 2
// remove from String: "$", ".", ","
let digitsOnly = filter("0123456789".contains)` // or, if you want to use regex, simply `let digitsOnly = replacingOccurrences(of: "[^0-9]", with: "", options: .regularExpression)`
// return formatted string
guard let value = Double(digitsOnly) {
return ""
}
return formatter.string(for: value / 100) ?? ""
}