flutter Sorting arraylist by Date

Question

In My streamBuilder I have Array list contains dates having format(dd-MM-yyyy). I want to arrange the list in ascending order. The code I used in StreamBuilder after getting Datasnapshot

 Map<dynamic, dynamic> data = snap.data.snapshot.value;

              List item = [];
              data.forEach(
                  (index, data) => item.add(
                      {"key": index, ...data}
                      )
              );
              item..sort((a,b)=>a['key'].compareTo(b['key']));

I am expecting result as 16-06-2020 17-06-2020 18-06-2020 19-06-2020 22-06-2020 04-07-2020

The result I am getting is 04-07-2020 16-06-2020 17-06-2020 18-06-2020 19-06-2020 22-06-2020

Solution

You'll need to parse your Strings to DateTimes. Since DateTime parse() method won't accept Strings in the format you provided, you can do something like this:

List<String> strings = ['04-07-2020', '17-06-2020', '16-06-2020', '19-06-2020', '18-06-2020', '22-06-2020'];
List<DateTime> dateTimes = [];
  
strings.forEach((string) {
  var splitted = string.split('-');
  var day = splitted[0];
  var month = splitted[1];
  var year = splitted[2];
  var formatted = '$year-$month-$day';
  dateTimes.add(DateTime.parse(formatted));
});
  
dateTimes.sort((a, b) => a.compareTo(b));

Just adapt it for your structure!

Comments

[julemand101]

What type is a['key']? It looks like it is a String which explain the weird sorting and not DateTime?

[Sunil]

@julemand101 yes it is child value read from Firebase Database. Can you please help me how to sort it in DateTime?

[Danaru]

You need to parse a['key'] and b['key'] to DateTime. api.flutter.dev/flutter/dart-core/DateTime/parse.html