[ios - swift] date to string, string to date

 public static func dateToString(dateFormat: String, date: Date) -> String {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = dateFormat
        return dateFormatter.string(from: date)
    }
    
    public static func stringTodate(dateFormat: String, stringDate: String) -> Date {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = dateFormat
        return dateFormatter.date(from: stringDate) ?? Date()
    }
    
    public static func changeDateFormat(beforeFormat: String, afterFormat: String, stringDate: String) -> String {
        let beforeFormatter = DateFormatter()
        beforeFormatter.dateFormat = beforeFormat
        
        let convertDate = beforeFormatter.date(from: stringDate) ?? Date()
        
        let afterFormatter = DateFormatter()
        afterFormatter.dateFormat = afterFormat
        return afterFormatter.string(from: convertDate)
    }