How to use a List as member variable in Flutter?

Question

I tried to define a class, which contains a List of a specific item-object, which will be populated within Constructor and will also receive new items at a later time:

class Repository {

  final List<Voting> _items = List<Voting>();

  Repository() {
    _items.add(Voting(1, "xyz", 0));
  }

  List<Voting> fetchItems() {
    return _items;
  }

}

However, Flutter is complaining:

The default 'List' constructor isn't available when null safety is enabled.

How to do?

Change the line ``final List _items = List();`` to ``List _items = new List();`` or ``List _items = [];`` — OMi Shah, May 24 '21 at 14:48
Does this answer your question? [Why List() constructor is not accessible in Dart's null safety?](https://stackoverflow.com/questions/63451506/why-list-constructor-is-not-accessible-in-darts-null-safety) — OMi Shah, May 24 '21 at 14:49

score 2 · Accepted Answer · answered May 24 '21 at 14:50

2

Try this:

final List<Voting> _items = <Voting>[];

instead of

final List<Voting> _items = List<Voting>();

answered May 24 '21 at 14:50

kforjan

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score 0 · Answer 2 · answered May 25 '21 at 09:24

0

List() is deprecated with Dart null safety, you can read more about it here.

You should either use [] or List.filled to create a list. For example:

final List<int> items = [];
final items = <int>[];

or

final List<int> items = List.filled(10, 0, growable: true)

answered May 25 '21 at 09:24

iDecode

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Use an example of objects please not `int` – Lutaaya Huzaifah Idris Jul 18 '21 at 18:55
@LutaayaHuzaifahIdris Replace `int` with the type of your object. – iDecode Jul 19 '21 at 05:28
What of the params, where I see ```(10, 0, growable: true)``` , what should be placed there, because it complains that they are for int. – Lutaaya Huzaifah Idris Jul 19 '21 at 10:23
@LutaayaHuzaifahIdris You should obviously be using the type of your object. I don't know what type it is. But you can create some mock data. – iDecode Jul 20 '21 at 08:42

How to use a List as member variable in Flutter?

2 Answers2