Different currencies have different standards for minor unit (ISO 4217: https://www.iso.org/iso-4217-currency-codes.html). e.g. USD minor units are displayed with two decimal places. JPY doesn’t have a minor unit. The solution is to store the value in minor units and make it client’s responsibility to do the conversion.

SwiftMoney.playground

import Foundation

let value = 10000 // Value stored in the database along with the currency code
let numberFormatter = NumberFormatter()
numberFormatter.numberStyle = .currency

numberFormatter.currencyCode = "USD"
print("\(Double(value)/pow(10, Double(numberFormatter.maximumFractionDigits)))") // 100.0

numberFormatter.currencyCode = "JPY"
print("\(Double(value)/pow(10, Double(numberFormatter.maximumFractionDigits)))") // 10000.0