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<Voting> _items = List<Voting>(); to List<Voting> _items = new List<Voting>(); or List<Voting> _items = []; — Omi Shah
– Omi Shah, Commented May 24, 2021 at 14:48
Does this answer your question? Why List() constructor is not accessible in Dart's null safety? — Omi Shah
– Omi Shah, Commented May 24, 2021 at 14:49
use final List<Voting> _items = []; to define an empty list — Mohammed Alfateh
– Mohammed Alfateh, Commented May 24, 2021 at 15:37

kforjan · Accepted Answer · 2021-05-24 14:50:16Z

2

Try this:

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

instead of

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

answered May 24, 2021 at 14:50

kforjan

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Comments

iDecode · Accepted Answer · 2021-05-25 09:24:50Z

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, 2021 at 9:24

iDecode

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4 Comments

Lutaaya Huzaifah Idris Over a year ago

Use an example of objects please not int

iDecode Over a year ago

@LutaayaHuzaifahIdris Replace int with the type of your object.

Lutaaya Huzaifah Idris Over a year ago

What of the params, where I see (10, 0, growable: true) , what should be placed there, because it complains that they are for int.

iDecode Over a year ago

@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.

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