Flutter Dart: how can I change the value of a class property in a list of Classes

Question

Hello I am having issue to understand how to manage properties of a class when it is part of a list of classes

Here are my classes

class BasketItem {
  final String itemDescription;
  final String itemNote;

  BasketItem(
      {this.itemDescription,
      this.itemNote});
}

class AppData {
  static final AppData _appData = new AppData._internal();

  List<BasketItem> basketList = [];
  factory AppData() {
    return _appData;
  }
  AppData._internal();
}

final appData = AppData();

And here is my List

List<Container> _buildBasketList() {
    return appData.basketList.map((bList) {
      var container = Container(
        child: Builder(
          builder: (context) => Dismissible(
            key: Key(UniqueKey().toString()),
            background: Container(
              margin: EdgeInsets.all(8.0),
              color: kColorAccent,
              child: Align(
                  alignment: Alignment(-0.90, 0.00),
                  child: Icon(Icons.add_comment)),
            ),
            onDismissed: (direction) {
                final newItemToAdd = BasketItem(
                    itemDescription: bList.itemDescription,
                    itemNote: 'xxxxx',);

                appData.basketList.add(newItemToAdd);

                setState(() {});
                appData.basketList.remove(bList);

            },
            child: Stack(...)
          ),
        ),
      );
      return container;
    }).toList();
  }

I would like to do the following: when onDismissed get executed I would like to amend the property itemNote to 'xxxxx'. How can I do it? At the moment I remove the BasketItem I have swiped and I create a new BasketItem and I add it to the list. The problem is that this does not seem efficient and it also add the item at the end of the list while I would like to keep it at the same position/index where it was.

Thanks

Answer 1

Approach 1

Make fields in BasketItem non final. So you can amend them.

class BasketItem {
  final String itemDescription;
  /*final*/ String itemNote;

  BasketItem(
      {this.itemDescription,
      this.itemNote});
}
// onDismissed will change itemNote.
....
    onDismissed: (direction) {
                setState(() {
                  bList.itemNote = 'xxxxx';
                });
            },
...

Approach 2

Replace list contents inline. Don't remove and add

List<Container> _buildBasketList() {
    return appData.basketList.asMap().map((index, bList) {
      var container = Container(
        child: Builder(
          builder: (context) => Dismissible(
            key: Key(UniqueKey().toString()),
            background: Container(
              margin: EdgeInsets.all(8.0),
              color: kColorAccent,
              child: Align(
                  alignment: Alignment(-0.90, 0.00),
                  child: Icon(Icons.add_comment)),
            ),
            onDismissed: (direction) {
                setState(() {
                  appData.basketList[index] = BasketItem(
                    itemDescription: bList.itemDescription,
                    itemNote: 'xxxxx',);
                });
            },
            child: Stack(...)
          ),
        ),
      );
      return container;
    }).toList();
  }