How to format a Double into Currency - Swift 3

You can use this string initializer if you want to force the currency to $:

String(format: "Tip Amount: $%.02f", tipAmount)

If you want it to be fully dependent on the locale settings of the device, you should use a NumberFormatter. This will take into account the number of decimal places for the currency as well as positioning the currency symbol correctly. E.g. the double value 2.4 will return "2,40 €" for the es_ES locale and "¥ 2" for the jp_JP locale.

let formatter = NumberFormatter()
formatter.locale = Locale.current // Change this to another locale if you want to force a specific locale, otherwise this is redundant as the current locale is the default already
formatter.numberStyle = .currency
if let formattedTipAmount = formatter.string(from: tipAmount as NSNumber) {
    tipAmountLabel.text = "Tip Amount: \(formattedTipAmount)"
}

How to do it in Swift 4:

let myDouble = 9999.99
let currencyFormatter = NumberFormatter()
currencyFormatter.usesGroupingSeparator = true
currencyFormatter.numberStyle = .currency
// localize to your grouping and decimal separator
currencyFormatter.locale = Locale.current

// We'll force unwrap with the !, if you've got defined data you may need more error checking

let priceString = currencyFormatter.string(from: NSNumber(value: myDouble))!
print(priceString) // Displays $9,999.99 in the US locale

You can to convert like that: this func convert keep for you maximumFractionDigits whenever you want to do

static func df2so(_ price: Double) -> String{
        let numberFormatter = NumberFormatter()
        numberFormatter.groupingSeparator = ","
        numberFormatter.groupingSize = 3
        numberFormatter.usesGroupingSeparator = true
        numberFormatter.decimalSeparator = "."
        numberFormatter.numberStyle = .decimal
        numberFormatter.maximumFractionDigits = 2
        return numberFormatter.string(from: price as NSNumber)!
    }

i create it in class Model then when you call , you can accecpt it another class , like this

 print("InitData: result convert string " + Model.df2so(1008977.72))
//InitData: result convert string "1,008,977.72"

The best way to do this is to create an NSNumberFormatter. (NumberFormatter in Swift 3.) You can request currency and it will set up the string to follow the user's localization settings, which is useful.

As an alternative to using a NumberFormatter, If you want to force a US-formatted dollars and cents string you can format it this way:

let amount: Double = 123.45

let amountString = String(format: "$%.02f", amount)

How to format a Double into Currency - Swift 3

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