Using Currency in Swift

Question

I am trying to create a function in Swift that accepts an integer as a param and returns a double in the locale currency e.g:

input : 1250

output : £12.50

input: 12500

output: £125.00

I noticed there is a third party library that supports this but unfortunately the repo is archived. The type of units used is the smallest type of currency which is minorUnits.

Network Call

/// GET - Retrive a feed of transactions during a certain period
static func get(accountUID: String, categoryUID: String, queryStartDate: String, queryEndDate: String , completionHandler: @escaping ([FeedItem], Error?) -> Void) {
    let sessionObject : URLSession = URLSession.shared
    let taskObject = sessionObject.dataTask(with: URLS().feedURLObject(accountUID,categoryUID,queryStartDate,queryEndDate)) { (Data, Response, Error) in
        guard Error == nil else {
            return
        }
        guard let Data = Data else {
            return
        }
        do {
            let feed = try JSONDecoder().decode(Feed.self, from: Data).feedItems.filter({ (item) -> Bool in
                item.direction == Direction.out
            })
            completionHandler(feed, nil)
        } catch let error  {
            print(error.localizedDescription)
        }
    }
    taskObject.resume()
}

Model Feed Struct Amount

struct Amount: Codable {
let currency: Currency
let minorUnits: Int}

Single Item JSON response

FeedItem(feedItemUid: "0651afe9-f568-4623-ad26-31974e26015c", categoryUid: "a68f9445-4d59-44e5-9c3f-dce2df0f53d2", amount: Banking_App.Amount(currency: Banking_App.Currency.gbp, minorUnits: 551), sourceAmount: Banking_App.Amount(currency: Banking_App.Currency.gbp, minorUnits: 551), direction: Banking_App.Direction.out, updatedAt: "2020-02-04T14:09:49.072Z", transactionTime: "2020-02-04T14:09:48.743Z", settlementTime: "2020-02-04T14:09:48.992Z", source: Banking_App.Source.fasterPaymentsOut, status: Banking_App.Status.settled, counterPartyType: Banking_App.CounterPartyType.payee, counterPartyUid: Optional("fed4d40b-9ccc-411d-81c7-870164876d04"), counterPartyName: Banking_App.CounterPartyName.mickeyMouse, counterPartySubEntityUid: Optional("d6d444c0-942f-4f85-b076-d30c2f745a6f"), counterPartySubEntityName: Banking_App.CounterPartySubEntityName.ukAccount, counterPartySubEntityIdentifier: "204514", counterPartySubEntitySubIdentifier: "00000825", reference: Banking_App.Reference.externalPayment, country: Banking_App.Country.gb, spendingCategory: Banking_App.SpendingCategory.payments)

Thanks

Answer 1

Currency codes are defined in the standard ISO 4217 and as part of the standard is the number of decimal digits used for each currency and since swift's NumberFormatter has a style for this ISO standard we can use it for this case.

Create an instance and set the style

let currencyFormatter = NumberFormatter()
currencyFormatter.numberStyle = .currencyISOCode

Set the currency code

currencyFormatter.currencyCode = "SEK"

Now currencyFormatter.minimumFractionDigit and currencyFormatter.maximumFractionDigits will both contain the number of decimals define for the given currency

So now we can put this together in a function for instance

func convertMinorUnits(_ units: Int, currencyCode: String) -> Decimal {
    let currencyFormatter = NumberFormatter()
    currencyFormatter.numberStyle = .currencyISOCode
    currencyFormatter.currencyCode = currencyCode.uppercased()

    return Decimal(units) / pow(10, currencyFormatter.minimumFractionDigits)
}

example

print(convertMinorUnits(551, currencyCode: "GBP")

5.51