Builder Design Pattern

import 'dart:developer';

class Date {
  final dynamic year;
  final dynamic month;
  final dynamic day;

  Date({
    required this.year,
    required this.month,
    required this.day,
  });

  void showDate() {
    String year = this.year.toString();
    String month = this.month.toString();
    String day = this.day.toString();

    log('Date: $year-$month-$day');
  }
}

class Time {
  final dynamic hour;
  final dynamic minute;
  final dynamic second;

  Time({
    required this.hour,
    required this.minute,
    required this.second,
  });

  void showTime() {
    String hour = this.hour.toString();
    String minute = this.minute.toString();
    String second = this.second.toString();

    log('Time: $hour:$minute:$second');
  }
}

class DateTime {
  final Date date;
  final Time time;

  DateTime({
    required this.date,
    required this.time,
  });

  void toDateTime() {
    date.showDate();
    time.showTime();
  }
}

class DateTimeBuilder {
  late DateTime dateTime;

  DateTimeBuilder({
    required this.dateTime,
  });

  void prepareDateTime() {
    dateTime.toDateTime();
  }
}

void main() {
  DateTimeBuilder dateTimeBuilder = DateTimeBuilder(
    dateTime: DateTime(
      date: Date(
        year: 2020,
        month: 1,
        day: 1,
      ),
      time: Time(
        hour: '1',
        minute: '1',
        second: '1',
      ),
    ),
  );

  dateTimeBuilder.prepareDateTime();
}