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Tito Soft
Asked: 2022-02-06 17:55:56 +0800 CST 2022-02-06 17:55:56 +0800 CST

create List or Map without repeated values ​​in flutter

  • 772

Good morning, a question made me balls when I wanted to do the following I have this structure

Data = [
    {"id" : 1, "nombre" : "A", "cantidad" : 20},
    {"id" : 1, "nombre" : "A", "cantidad" : 30},
    {"id" : 2, "nombre" : "B", "cantidad" : 15},
    {"id" : 2, "nombre" : "B", "cantidad" : 10},
    {"id" : 3, "nombre" : "C", "cantidad" : 20}]

I want to get this result only from the id's without duplicate

R=[{"id" : 1}, {"id" : 2}, {"id" : 3}]either

R = [1, 2, 3]
lista

1 Answers

  1. Best Answer

    Simple, in the long form:

      final data = [
    {"id": 1, "nombre": "A", "cantidad": 20},
    {"id": 1, "nombre": "A", "cantidad": 30},
    {"id": 2, "nombre": "B", "cantidad": 15},
    {"id": 2, "nombre": "B", "cantidad": 10},
    {"id": 3, "nombre": "C", "cantidad": 20}
  ];

  Set<int> ids = {};
  for (Map item in data) {
    ids.add(item['id']);
  }
  final idsArray = ids.toList();
  print(idsArray);

    In the short form:

      final data = [
    {"id": 1, "nombre": "A", "cantidad": 20},
    {"id": 1, "nombre": "A", "cantidad": 30},
    {"id": 2, "nombre": "B", "cantidad": 15},
    {"id": 2, "nombre": "B", "cantidad": 10},
    {"id": 3, "nombre": "C", "cantidad": 20}
  ];

  final idsArray = data.map((item) => item['id']).toSet().toList();
  print(idsArray);

    The trick is to use toSet()so that it adds the elements without repeating.

    More info: https://api.flutter.dev/flutter/dart-core/Set-class.html

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