Question 75700 in Flutter Question posted in
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Getting list of unique objects from list of duplicates in Dart – Flutter

I have the following List of Map Objects:

[
  {
    "name": "Sameera Tennakoon",
    "userID": "7c770f8d-hju4-4ddd-b5cb-f3d0caba2bb3",
    "type": "CASHIER"
  },
  {
    "name": "Sam Perera",
    "userID": "7c770f8d-f6f4-3eee-b5cb-f3d0caba2bb3",
    "type": "CASHIER"
  },
  {
    "name": "Uma Jackson",
    "userID": "7c770f8d-f6f4-4ddd-5634-f3d0caba2bb3",
    "type": "CASHIER"
  },
  {
    "name": "Anu Ima",
    "userID": "7c770f8d-f6f4-4ddd-lksa-f3d0caba2bb3",
    "type": "CASHIER"
  },
  {
    "name": "Sameera Tennakoon",
    "userID": "7c770f8d-hju4-4ddd-b5cb-f3d0caba2bb3",
    "type": "CASHIER"
  }
];

I want to remove the duplicate items from this List. How can I do that in Flutter?

P.S. – .toSet() and .toList() methods did not work in this case.

Tags:

4

Answers


  1. 0

    Suppose you store the entire list in a List l1=[. . .], use toSet() for removing duplicates:

    l1.toSet().toList();
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  2. 0

    If it’s sufficient to only check on equal userIDs you could do this:

    import 'package:collection/collection.dart';

void main(){
  final list = [
    {
      "name": "Sameera Tennakoon",
      "userID": "7c770f8d-hju4-4ddd-b5cb-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Sam Perera",
      "userID": "7c770f8d-f6f4-3eee-b5cb-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Uma Jackson",
      "userID": "7c770f8d-f6f4-4ddd-5634-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Anu Ima",
      "userID": "7c770f8d-f6f4-4ddd-lksa-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Sameera Tennakoon",
      "userID": "7c770f8d-hju4-4ddd-b5cb-f3d0caba2bb3",
      "type": "CASHIER"
    }
  ];

  final result = groupBy(list, (Map e) => e['userID']).values.map((e) => e.first).toList();
}
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  3. 0

    Write a method which will filter items by specific field occurrence in Set:

    List<Map<String, dynamic>> filterListByKey (
  List<Map<String, dynamic>> list,
  String key
) {
  Set ids = Set<String>();
  
  return list.where((e) {
    if (ids.contains(e[key].toString())) {
      return false;
    }
    
    ids.add(e[key].toString());
    return true;
  }).toList();
}

    and use it:

    void main() {
  final List<Map<String, dynamic>> users = [
    {
      "name": "Sameera Tennakoon",
      "userID": "7c770f8d-hju4-4ddd-b5cb-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Sam Perera",
      "userID": "7c770f8d-f6f4-3eee-b5cb-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Uma Jackson",
      "userID": "7c770f8d-f6f4-4ddd-5634-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Anu Ima",
      "userID": "7c770f8d-f6f4-4ddd-lksa-f3d0caba2bb3",
      "type": "CASHIER"
    },
    {
      "name": "Sameera Tennakoon",
      "userID": "7c770f8d-hju4-4ddd-b5cb-f3d0caba2bb3",
      "type": "CASHIER"
    }
  ];
  final uniqueUsers = filterListByKey(users, 'userID');
  
  print(uniqueUsers);
  
}

    You can test it here

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  4. 0

    One way to remove duplicates from a List of Map objects in Flutter without using a set is by iterating over the List and adding each Map object to a new List only if it does not already exist in the new List.

    final List<Map<String, dynamic>> originalList = [...];
final List<Map<String, dynamic>> newList = [];

originalList.forEach((map) {
  if (!newList.any((newMap) => newMap['userID'] == map['userID'])) {
    newList.add(map);
  }
});

print(newList);
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