JsonDecode to List<Object> from SharedPreferences - json

Question

I have a list of strings which is held in an object and is stored in shared preferences.
I have used ScopedModel for my state management and I am trying to get it to read the list from the shared preferences from here.
class Item {
String _weight;
String _name;
String _id;
Item(this._weight, this._name, this._id);
Item.fromJson(Map<String, dynamic> m) {
_weight = m['weight'] as String;
_name = m['name'] as String;
_id = m['id'] as String;
}
String get id => _id;
String get name => _name;
String get weight => _weight;
Map<String, dynamic> toJson() => {
'weight': _weight,
'name': _name,
'id': _id,
};
}
My Model in the ScopedModel folder which is passed down;
mixin ListItem on Model {
String itemKey = 'itemKey';
List<Item> _items = [];
List<Item> get items {
return List.from(_items);
}
Future<Null> readList() async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
final data = json.decode(prefs.getString(itemKey).toString());
final item = List<Item>.from(data.map((i) => Item.fromJson(i)));
_items = item;
print(jsonDecode(prefs.getString(itemKey)));
notifyListeners();
}
Future<Null> addItem({String id, String name, String weight}) async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
final Item item = Item(
id,
name,
weight,
);
_items.add(item);
prefs.setString(itemKey, jsonEncode(_items));
notifyListeners();
}
Future<Null> deleteProduct() async {
notifyListeners();
}
}
Part of my stateful widget which runs the initState to call the list from sharedPreferences
class _ListItemsState extends State<ListItems> {
final MainModel _model = MainModel();
final TextEditingController controller = TextEditingController();
#override
void initState() {
_model.readList();
super.initState();
}
#override
Widget build(BuildContext context) {
return ScopedModelDescendant<MainModel>(
builder: (BuildContext context, Widget child, MainModel model) {
return Scaffold(
appBar: AppBar(),
body: CustomScrollView(
slivers: <Widget>[
SliverList(
delegate: SliverChildListDelegate([
TextField(
controller: controller,
),
FlatButton(
child: Text('Submit'),
onPressed: () {
model.addItem(
id: controller.text,
name: controller.text,
weight: controller.text,
);
},
),
]),
),
model.items.length > 0
? SliverList(
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Dismissible(
key: Key(model.items[index].id),
background: Container(
color: Colors.redAccent,
),
onDismissed: (DismissDirection direction) {
model.deleteProduct();
},
child: ListTile(
leading: Text(model.items[index].name),
trailing: Text(model.items[index].weight),
onTap: () {},
),
);
},
childCount: model.items.length,
),
)
: SliverFillRemaining(),
],
));
},
);
}
}
My issue is that on the initState the list doesn't appear from the readList() - I'm not sure what I am doing wrong as when I run the print(json.decode(prefs.getString(itemKey)); it calls the list of items that are held from the sharedPreferences as [{weight: HelloWorld, name: HelloWorld, id: HelloWorld}] which looks like it should be fine to decode.
Can anyone help point out what I'm doing wrong? Thanks in advance.

Answer 1

In your code, you have 2 different models:
final MainModel _model = MainModel();
and another model from builder
builder: (BuildContext context, Widget child, MainModel model)
It looks like that there is no connection/link/map between _model and model. You have to link them together like in this discussion.