Flutter: how to create Map from firebase snapshot and merge data with same key-CodePudding

i want to use table_calendar with firebase data, but still having issue passing events into the widget ....

Sample structure of firebase data:

{
'date' : 26 Jun
'name' : A

'date' : 26 Jun
'name' : B

'date' : 11 Feb
'name' : C

}

i want to create the Map in this way:

{
    '26 Jun' : [{'date' : 26 Jun, 'name' : A} , {'date' : 26 Jun, 'name' : B}]
    '11 Feb' : [{'date' : 11 Feb, 'name' : C}]
    
    }

below code was trying to use Map.fromIterable but i'm not sure how to merge data with same key...

final _kEventSource = Map<DateTime, List<dynamic>>.fromIterable(bookings,
        key: (item) => item['date'].toDate(),
        value: (item) => List.generate(1, (index) => item))

================================================================

UPDATE:

    var newMap = groupBy(bookings, (obj) => (obj as Map)['date'].toDate()).map((k, v) => MapEntry<DateTime, List<dynamic>>(
        k,
        v.map((item) {
          item.remove('date');
          return item;
        }).toList()));
    print(newMap);


    final kEvents = LinkedHashMap<DateTime, List<dynamic>>(equals: isSameDay, hashCode: getHashCode)
      ..addAll(newMap);
    return kEvents[day] ?? [];
  }

i cannot execute the code above , seeing error with

The method 'toDate' was called on null.
Receiver: null
Tried calling: toDate()

CodePudding user response：

With the collection package you can group by date. Try this code:

import "package:collection/collection.dart";

void main() {
  var data = [
    {'date': "26 Jun", 'name': "A"},
    {'date': "26 Jun", 'name': "A"},
    {'date': "11 Feb", 'name': "C"},
  ];

  var newMap = groupBy(data, (Map obj) => obj['date']).map((k, v) => MapEntry(
      k,
      v.map((item) {
        item.remove('date');
        return item;
      }).toList()));
  print(newMap);
}

Output:

{26 Jun: [{name: A}, {name: A}], 11 Feb: [{name: C}]}