CODEWITHSUNDEEP
flutterdart
user2682025
user2682025

Reputation: 804

Compare elements in two lists and make a new List in Dart

I have two lists and I want to make a new list by comparing the two lists and the new list should only contain those elements that contain in each of them.

List1=[[id: 1, label: 'cocoa'],[id: 2, label: 'apple'],[id: 3, label: 'cherry'],[id: 4, label: 'banana'],[id: 5, label: 'melon'],[id: 6, label: 'orange'],[id: 7, label: 'pineapple'],[id: 8], label: 'strawberry']
List2=[2,5,7,8]
expectedList = [[id: 2, label: 'apple'],[id: 5, label: 'melon'],[id: 7, label: 'pineapple'],[id: 8], label: 'strawberry']]

And the real code down below:

"options": [
                    {
                        "id": 58,
                        "label": "cocoa",
                        "swatch_value": null,
                        "products": [
                            118
                        ]
                    },
                    {
                        "id": 59,
                        "label": "dark chocolate",
                        "swatch_value": null,
                        "products": [
                            120,
                            127
                        ]
                    },
                    {
                        "id": 60,
                        "label": "apple",
                        "swatch_value": null,
                        "products": [
                            121,
                            128
                        ]
                    },
                    {
                        "id": 61,
                        "label": "milk",
                        "swatch_value": null,
                        "products": [
                            122
                        ]
                    },
                    {
                        "id": 62,
                        "label": "coconut",
                        "swatch_value": null,
                        "products": [
                            130
                        ]
                    },
                    {
                        "id": 65,
                        "label": "cherry",
                        "swatch_value": null,
                        "products": [
                            126
                        ]
                    }
                ]

So the first list would contain the json above, and the second list contains the numbers below that equals to some of the ID.

List<int> secondList = [58, 59, 60, 61];

Now when I want to generate a new list by comparing the secondList with the ID's of the first list, the third list is empty.

List thirdList = firstList.options.where((element) => secondList.contains(element.id)).toList();

Upvotes: 0

Views: 2766

Answers (1)

Ουιλιαμ Αρκευα
Ουιλιαμ Αρκευα

Reputation: 6257

  var list1 = [1,2,3,4,5,6,7,8];
  var list2 = [2,5,7,8];
  var expectedList = list1.toSet().intersection(list2.toSet()).toList();

  print(expectedList.toString());

More information here.

Respect to your info:

  var dataList = data['options'];
  var firstList = List<int>.generate(dataList.length, (i) => dataList[i]['id']);
  var secondList = [58, 59, 60, 61];
  var thirdList = firstList.toSet().intersection(secondList.toSet()).toList();
  var filtered = dataList.where((e) => thirdList.contains(e['id'])).toList();
  print(filtered.toString());

where:

const data = {
  "options": [
...
  ]
};

The result is:

[{id: 58, label: cocoa, swatch_value: null, products: [118]}, {id: 59, label: dark chocolate, swatch_value: null, products: [120, 127]}, {id: 60, label: apple, swatch_value: null, products: [121, 128]}, {id: 61, label: milk, swatch_value: null, products: [122]}]

Upvotes: 3

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