How can converting a String with a comma to a String with a decimal

extension String { static let numberFormatter = NumberFormatter() var doubleValue: Double { String.numberFormatter.decimalSeparator = "." if let result = String.numberFormatter.number(from: self) { return result.doubleValue } else { String.numberFormatter.decimalSeparator = "," if let result = String.numberFormatter.number(from: self) { return result.doubleValue } } return 0 } }

"2.25".doubleValue // 2.25 "2,25".doubleValue // 2.25

let price = "2,25" let costString = String(format:"%.2f", price.doubleValue) // "2.25"