DateFormatterExample.swift

//call the method
let convertedDateString = self.dateFromString("2019-05-20", fromFormat: "yyyy-MM-dd", toFormat: "dd-MM-yyyy")
print(convertedDateString ?? "Failed to convert date")



func dateFromString(_ dateString:String, fromFormat:String, toFormat: String) -> String? {

        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = fromFormat

        guard let fromDate = dateFormatter.date(from: dateString) else { return nil }
        dateFormatter.dateFormat = toFormat

        return dateFormatter.string(from: fromDate)
}