Flutter : Generate List of total sales for each month from another list of DateTime

I have a list of daily sales which includes "DateTime" & "Int" for each entry.

final data = [
      DailySales(2022-03-10 00:00:00.000, 200),
      DailySales(2022-03-09 00:00:00.000, 255),
      DailySales(2022-02-08 00:00:00.000, 100),
      DailySales(2022-02-10 00:00:00.000, 520),
      DailySales(2022-01-08 00:00:00.000, 100),
      DailySales(2022-01-10 00:00:00.000, 520),
    ];

class DailySales {
  final DateTime day;
  final int sales;

  DailySales(this.day, this.sales);
}

Now Based on the above list, I need to dynamically generate a new list that shall includes one entry per Month of month name and the total sales for that month.

as shown in the model below:

class MonthlySales {
  final String month;
  final int sales;

  MonthlySales(this.month, this.sales);
}

Can some help on this please

you can do it like this:

main() {
  final data = [
    DailySales(DateTime.parse("2022-03-10 00:00:00.000"), 200),
    DailySales(DateTime.parse("2022-03-09 00:00:00.000"), 255),
    DailySales(DateTime.parse("2022-02-08 00:00:00.000"), 100),
    DailySales(DateTime.parse("2022-02-10 00:00:00.000"), 520),
    DailySales(DateTime.parse("2022-01-08 00:00:00.000"), 100),
    DailySales(DateTime.parse("2022-01-10 00:00:00.000"), 520),
  ];

  Map tempMap = Map();

  for (DailySales item in data) {
    if (tempMap[item.day.month] == null) {
      tempMap[item.day.month] = item.sales;
    } else {
      tempMap[item.day.month] = tempMap[item.day.month] + item.sales;
    }
  }
  List monthlySales = [];
  for (int i = 1; i <= 12; i++) {
    if (tempMap[i] != null)
      monthlySales.add(MonthlySales(i.toString(), tempMap[i]));
  }
  print(monthlySales);
}

class DailySales {
  final DateTime day;
  final int sales;

  DailySales(this.day, this.sales);
}

class MonthlySales {
  final String month;
  final int sales;

  MonthlySales(this.month, this.sales);
  @override
  String toString() {
    // TODO: implement toString
    return "month " + month + " sales " + sales.toString();
  }
}

the output would look like:

[month 1 sales 620, month 2 sales 620, month 3 sales 455]