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

CodePudding user response：

Here is what you need to do:-

void main() {
  final data = [
    DailySales(day: DateTime(2022, 03, 09), sales: 200),
    DailySales(day: DateTime(2022, 03, 08), sales: 255),
    DailySales(day: DateTime(2022, 03, 07), sales: 100),
    DailySales(day: DateTime(2022, 03, 04), sales: 520),
    DailySales(day: DateTime(2022, 03, 02), sales: 100),
    DailySales(day: DateTime(2022, 03, 03), sales: 520),
  ];

  List<MonthlySales> monthlySales = data
      .map((dailySale) => MonthlySales(
          month: dailySale.day.month.toString(), sales: dailySale.sales))
      .toList();

  print(monthlySales.runtimeType);
  print(monthlySales.toString());
}

class DailySales {
  final DateTime day;
  final int sales;

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

class MonthlySales {
  final String month;
  final int sales;

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

And the output is below:-

List<MonthlySales>
[Instance of 'MonthlySales', Instance of 'MonthlySales', Instance of 'MonthlySales', Instance of 'MonthlySales', Instance of 'MonthlySales', Instance of 'MonthlySales']

Dart collections provide many such rich methods like, map methods above to make the business logics simple.

Once visit it for more help.

CodePudding user response：

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]

CodePudding user response：

You can use this package to groupdata collection

collection: ^1.15.0

 List<MonthlySales> OrderSalebymonth() {
  List<String> months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];
  final datas = [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),];
  List<MonthlySales> monthlist = [];
  var groupBy2 = groupBy(datas, (DailySales sale) => sale.day.month);
  groupBy2.forEach((key, value) {print("=================Month:$key ${months[key - 1]}=============");value.forEach((element) {monthlist.add(MonthlySales(months[key - 1], element.sales));print(element.sales.toString());});});
  return monthlist;
}
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);
}

Expected output

=================Month:3 March=============
200
255
=================Month:2 February=============
100
520
=================Month:1 January=============
100
520