Flutter Pass Function With Generic Parameter - flutter

Question

I am trying to write a Typehead package. In case of that, I need to pass functions with generic parameters but I am getting a type error.
Here is my simplified code:
Models:
class BaseModel {
BaseModel({required this.title});
String title;
}
class SearchModel extends BaseModel {
SearchModel({required super.title, required this.myText});
String myText;
}
TypeHead Class:
class HorizontalTypeHead<T extends BaseModel> extends StatefulWidget {
const HorizontalTypeHead({
Key? key,
required this.onLookup,
required this.onSelected,
}) : super(key: key);
final Future<Iterable<T>> Function(String value) onLookup;
final Function(T model) onSelected;
#override
State<HorizontalTypeHead> createState() => _HorizontalTypeHeadState<T>();
}
class _HorizontalTypeHeadState<T extends BaseModel> extends State<HorizontalTypeHead> {
Iterable<T> _data = [];
List<Widget> renderColumn(BuildContext context) {
List<Widget> list = [
TextField(
onChanged: (String? val) async {
if (val != null) {
_data = await widget.onLookup(val) as Iterable<T>;
setState(() {});
}
},
),
];
if (_data.isNotEmpty) {
list.add(
SizedBox(
height: 100,
child: ListView(
scrollDirection: Axis.horizontal,
children: _data
.map((e) => ResultWidget<T>(
model: e, onSelected: widget.onSelected))
.toList(),
),
),
);
}
return list;
}
#override
Widget build(BuildContext context) {
return Column(children: renderColumn(context));
}
}
Result Widget:
class ResultWidget<T extends BaseModel> extends StatelessWidget {
const ResultWidget({required this.model, required this.onSelected, Key? key})
: super(key: key);
final T model;
final Function(T selected) onSelected;
#override
Widget build(BuildContext context) {
return InkWell(
onTap: () => onSelected(model),
child: Container(
color: Colors.red,
height: 100,
width: 100,
child: Text(model.title),
));
}
}
My main goal is to access data in SearchModel (myText field). But when I am assigning SearchModel as type, I get a type error.
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
Future<Iterable<SearchModel>> onLookup(String pattern) async {
return [SearchModel(title: "title", myText: "myText")];
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(),
body: HorizontalTypeHead<SearchModel>(
onSelected: ((model) => print(model.myText)), //I need to get myText
onLookup: onLookup,
),
));
}
}
_TypeError (type '(SearchModel) => void' is not a subtype of type '(BaseModel) => dynamic')
I would like to ask what I need to do for accessing SearchModel without any error from main class. Thanks in advance!

Answer 1

I just made generic my state class and solved it :)
class _HorizontalTypeHeadState<T extends BaseModel>
extends State<HorizontalTypeHead<T>>
instead of
class _HorizontalTypeHeadState<T extends BaseModel>
extends State<HorizontalTypeHead>