How to Sort List based on custom Date Dart

Question

I have the following function that sort List based on Date but if DateTime before firstDay of month it create double list

what I want is it sort list based on first day of month and remove all item before firstday


List expenseData= [

 {id: 1242, detail: milk, amount: $5, date: 2021-06-21 00:00:00:000},
 {id: 1242, detail: egg, amount: $2, date: 2021-05-15 00:00:00:000},
 {id: 1243, detail: bread, amount: $3, date: 2021-05-13 00:00:00:000},
 {id: 1244, detail: butter, amount: $7, date: 2021-05-22 00:00:00:000},
 {id: 1247, detail: butter, amount: $7, date: 2021-06-10 00:00:00:000},

];

pieDatathisMonth() {
    var now = DateTime.now();
    var firstDayMonth = DateTime(now.year, now.month, 1);
    var sortExpData = expenseData;
    sortExpData.sort((d1, d2) {
      return d1.date.compareTo(firstDayMonth);
    });
    sortExpData.toList();
    thisMonthExpense.addAll(sortExpData);
    update();
  }

Your sort callback is wrong. It must compare d1 to d2, not d1 to some other date. Otherwise sort() cannot properly order d1 relative to d2. If you want to remove all dates before a cut-off date, it'd be better to filter your list with expenseData.where((dateTime) => dateTime.compareTo(firstDayOfMonth) >= 0) and then sort it. — jamesdlin
– jamesdlin, Commented Jun 28, 2021 at 6:37
nothing error showed because the problem is my filtering I see it thanks for your clue — Tony Hart
– Tony Hart, Commented Jun 28, 2021 at 9:38

Guillaume Roux · Accepted Answer · 2021-06-28 07:52:13Z

1

Here is a fix to your sort method. I've made some DateTime cast because my expenseData is formatted as Map<String, dynamic>.

void pieDatathisMonth() {
  var now = DateTime.now();
  var firstDayMonth = DateTime(now.year, now.month, 1);
  var sortExpData = List<Map<String, dynamic>>.from(expenseData);
  
  // remove all data before firstday because you don't need to sort them.
  sortExpData.removeWhere((e) => (e['date'] as DateTime).isBefore(firstDayMonth));
  
  sortExpData.sort((d1, d2) {
    return (d1['date'] as DateTime).compareTo(d2['date'] as DateTime);
  });
  sortExpData.toList();
  thisMonthExpense.addAll(sortExpData);
  update();
}

answered Jun 28, 2021 at 7:52

Guillaume Roux

7,3771 gold badge20 silver badges48 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to Sort List based on custom Date Dart

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related