Render conditional section using factory and COR patterns

conditional_section.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String _name = 'scale';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Test'),
      ),
      body: Center(
        child: Builder(
          builder: (context) {
            QuestionSection? section;

            try {
              section = QuestionSection.create(_name);
            } catch (err) {
              print(err);
            }

            return section ?? Container();
          },
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => setState(() => _name = _name == 'scale' ? 'choice' : 'scale'),
        backgroundColor: Colors.blue,
        child: const Icon(Icons.change_circle),
      ),
    );
  }
}

abstract class QuestionSection implements Widget {
  static final QuestionSectionAbstractResolver _resolvers = ScaleQuestionResolver()..setNext(ChoiceQuestionResolver());

  factory QuestionSection.create(String name) {
    var section = _resolvers.resolve(name);

    if (section != null) {
      return section;
    } else {
      throw Exception('Unable to create instance for name: $name');
    }
  }

  final String name;

  const QuestionSection(this.name);
}

class ScaleQuestionSection extends StatelessWidget implements QuestionSection {
  @override
  final String name;

  const ScaleQuestionSection({
    Key? key,
    required this.name,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.pinkAccent,
      height: 300,
      width: 300,
      child: Text(
        'Name $name',
        style: const TextStyle(color: Colors.white),
      ),
    );
  }
}

class ChoiceQuestionSection extends StatelessWidget implements QuestionSection {
  @override
  final String name;

  @override
  const ChoiceQuestionSection({Key? key, required this.name}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.blueGrey,
      height: 300,
      width: 300,
      child: Text(
        'Name $name',
        style: const TextStyle(color: Colors.white),
      ),
    );
  }
}

abstract class QuestionSectionAbstractResolver {
  QuestionSectionAbstractResolver? _nextResolver;

  QuestionSectionAbstractResolver setNext(QuestionSectionAbstractResolver resolver) {
    _nextResolver = resolver;
    return resolver;
  }

  QuestionSection? resolve(String name) {
    if (_nextResolver != null) {
      return _nextResolver!.resolve(name);
    }

    return null;
  }
}

class ScaleQuestionResolver extends QuestionSectionAbstractResolver {
  ScaleQuestionResolver();

  @override
  QuestionSection? resolve(String name) {
    if (name == 'scale') {
      return ScaleQuestionSection(name: name);
    }

    return super.resolve(name);
  }
}

class ChoiceQuestionResolver extends QuestionSectionAbstractResolver {
  ChoiceQuestionResolver();

  @override
  QuestionSection? resolve(String name) {
    if (name == 'choice') {
      return ChoiceQuestionSection(name: name);
    }

    return super.resolve(name);
  }
}