Error: Could not find the correct ScopedModel when using ScopedModel.of(context)

Question

As an outsider looking into flutter state management, I liked the idea of using scoped_model for state management as recommended in flutter.dev. I have a rewrite of the counter app running. I am able to access the model properties using ScopedModelDescendant<CounterModel>, but I am having troubles accessing the model properties using ScopedModel.of<CounterModel>(context). Could someone please advice what I might be doing wrong? I have a hunch that it could be where the ScopedModel is in my widget tree. My code and error message follows.

main.dart

import 'package:flutter/material.dart';
import 'package:scoped_model/scoped_model.dart';
import 'package:second/model/counter_model.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Widget build(context) {
    return ScopedModel(
      model: new CounterModel(),
      child: Scaffold(
          appBar: AppBar(
            title: Text('ScopedModel'),
          ),
          body: ScopedModelDescendant<CounterModel>(
            builder: (context, child, value) {
              return Text("Pressed ${value.counter} times");
            },
          ),
          floatingActionButton: buildFab1()),
    );
  }

  Widget buildFab1() {
    return ScopedModelDescendant<CounterModel>(
      builder: (context, child, model) => FloatingActionButton(
            child: Icon(Icons.add),
            onPressed: model.incrementCounter,
          ),
    );
  }

  Widget buildFab2(BuildContext context) {
    return FloatingActionButton(
      child: Icon(Icons.add),
      onPressed: ScopedModel.of<CounterModel>(context).incrementCounter,
    );
  }
}

model/counter_model.dart

import 'package:scoped_model/scoped_model.dart';

class CounterModel extends Model {
  int _counter = 0;

  int get counter => _counter;

  void incrementCounter() {
    _counter++;
    notifyListeners();
  }
}

In main.dart, if I use buildFab2(context) instead of buildFab1(), I get the following error


flutter: The following ScopedModelError was thrown building ScopedModelDescendant<Model>(dirty):
flutter: Error: Could not find the correct ScopedModel.
flutter:
flutter: To fix, please:
flutter:
flutter:   * Provide types to ScopedModel<MyModel>
flutter:   * Provide types to ScopedModelDescendant<MyModel>
flutter:   * Provide types to ScopedModel.of<MyModel>()
flutter:   * Always use package imports. Ex: `import 'package:my_app/my_model.dart';
flutter:

I took a look at a few SO questions, but none helped.

score 5 · Accepted Answer · answered Apr 26 '19 at 09:37

Yes, that because, the context you pass will not have a ScopedModel of CounterModel.

What you can do is wrap your buildFab2 inside a Builder widget which will provide you with a context having ScopedModel with CounterModel as parent.

Like:

Builder(
    builder: (context){
      return buildFab2(context);
    },
  )

You app will look like:

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Widget build(context) {
    return ScopedModel(
      model: new CounterModel(),
      child: Scaffold(
        appBar: AppBar(
          title: Text('ScopedModel'),
        ),
        body: ScopedModelDescendant<CounterModel>(
          builder: (context, child, value) {
            return Text("Pressed ${value.counter} times");
          },
        ),
        floatingActionButton: Builder(
          builder: (context) {
            // return buildFab1() if fab one required
            return buildFab2(context);
          },
        ),
      ),
    );
  }

  Widget buildFab1() {
    return ScopedModelDescendant<CounterModel>(
      builder: (context, child, model) => FloatingActionButton(
            child: Icon(Icons.add),
            onPressed: model.incrementCounter,
          ),
    );
  }

  Widget buildFab2(BuildContext context) {
    return FloatingActionButton(
      child: Icon(Icons.add),
      onPressed: ScopedModel.of<CounterModel>(context).incrementCounter,
    );
  }
}

Hope that helps!

Thanks, sure enough it works. I don't however understand how `BuildContext` is built and why does it not register the `ScopedModel` of `CounterModel`. Can you recommend some resources I might be able to look at? — Bishal, Apr 26 '19 at 12:53
I'd always prefer to look at the docs first, [here](https://docs.flutter.io/flutter/widgets/BuildContext-class.html) it is. Some examples can be found [here](https://flutterbyexample.com/build-context-class/). — Hemanth Raj, Apr 27 '19 at 05:19

score 1 · Answer 2 · answered Jan 04 '21 at 17:53

You need to add the scoppedmodel in the main.dart like this:

@override
  Widget build(BuildContext context){
    return ScopedModel<UserModel>(
        model: UserModel(),
        child: MaterialApp(
            title: "Quiz Flamengo",
            debugShowCheckedModeBanner: false,
            home: Scaffold(
              body: HomeScreen(),
            )
        )
    );
  }

Error: Could not find the correct ScopedModel when using ScopedModel.of(context)

2 Answers2