Swift convert Currency string to double

Question

I have a string, "$4,102.33" that needs to be converted to double. This will always be US. My only way is a hack to strip out the $ and , and then convert to double. Seems like NSFormatter only lets me convert TO a currency and not from it. Is there a built-in function or better way than just removing the $ and ,? prior to converting it to double?

Tucker

Side note, avoid using Double for currency: #3730519 – Tampere

NSNumberFormatter will easily convert that string to a number if you set it up properly. Show your attempt use of NSNumberFormatter in your question. – Selina

Argh - I only saw the .string method. Didn't realize there was a .number method. :-( – Tucker

Answer 1

NumberFormatter can convert to and from string. Also Double cannot represent certain numbers precisely since it's base-2. Using Decimal is slower but safer.

let str = "$4,102.33"

let formatter = NumberFormatter()
formatter.numberStyle = .currency

if let number = formatter.number(from: str) {
    let amount = number.decimalValue
    print(amount)
}

Copyread

Note - If the string is always going to be formatted as USD, you will need to set the formatter's locale to en_US. If you don't, the string won't be parsed properly in most other locales. – Selina

Answer 2

To convert from String to NSNumber for a given currency is easy:

let formatter = NumberFormatter()
formatter.numberStyle = .currency
formatter.locale = Locale(identifier: "en_US")
let number = formatter.number(from: string)

To get your number as a Double or as a Decimal (preferred) is then direct:

let doubleValue = number?.doubleValue
let decimalValue = number?.decimalValue

Aubin