【Flutter/Dart】Bloc !! <アーキテクチャ>

dependencies:
  bloc: ^8.0.3
  flutter_bloc: ^8.0.1

lib/
  main.dart
  counter_page.dart
  cubit/
    counter_cubit.dart

import 'package:counter_cubit/counter_cubit.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

class MyHomePage extends StatelessWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;
  
    @override
  Widget build(BuildContext context) {
    // BlocProviderでWidgetを囲む。
    return BlocProvider(
      // create でビジネスロジックをおきます
      // こうやって囲むと配下のWidgetでcreateのビジネスロジックが使えます。
      // contextに処理を格納してます。
      create: (_) => CounterCubit(),
      child: Scaffold(
        appBar: AppBar(
          title: Text(title),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              const Text(
                'You have pushed the button this many times:',
              ),
	      // BlocBuilderで囲むことでStatefullWidgetのsetStateを実現しています。
              BlocBuilder<CounterCubit, int>(
                builder: (context, state) => Text(
                  '$state',
                  style: Theme.of(context).textTheme.headline4,
                ),
              ),
            ],
          ),
        ),
        floatingActionButton: Column(
          mainAxisAlignment: MainAxisAlignment.end,
          children: [
            FloatingActionButton(
	      // contextに格納されたクラスを呼び出すことでファンクションを実行します。
              onPressed: context.read<CounterCubit>().countUp,
              tooltip: 'Increment',
              child: const Icon(Icons.add),
            ),
            const SizedBox(
              height: 8,
            ),
            FloatingActionButton(
              onPressed: context.read<CounterCubit>().countDown,
              tooltip: 'decriment',
              child: const Icon(
                Icons.exposure_minus_1,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter_bloc/flutter_bloc.dart';

// Cubitクラスをextendsします。<>の中にモデルなどを設定して使います。※今回はint
class CounterCubit extends Cubit<int> {
  CounterCubit() : super(0);

  void countUp() => emit(state + 1);

  void countDown() => emit(state - 1);
}

import 'package:flutter_bloc/flutter_bloc.dart';

abstract class CounterEvent {}
class CounterIncrementPressed extends CounterEvent {}
class CounterdecrementPressed extends CounterEvent {}

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<CounterIncrementPressed>((event, emit) => emit(state + 1));
    on<CounterdecrementPressed>((event, emit) => emit(state - 1));
  }
}

Navigator.push(
    context,
    MaterialPageRoute(
      builder: (_) => BlocProvider.value(
	value: BlocProvider.of<CounterCubit>(context),
	child: const SamplePage(),
      ),
    ),
  );

dev_dependencies:
  bloc_test: ^9.0.3 #最新版

import 'package:bloc_test/bloc_test.dart';
import 'package:counter_cubit/counter_cubit.dart';
import 'package:flutter_test/flutter_test.dart';

//モック用のクラスを準備します。
class MockCounterCubit extends MockCubit<int> implements CounterCubit {}

void main() {
  mainCubit();
}

void mainCubit() {
  group('whenListen', () {
    test("Let's mock the CounterCubit's stream!", () {
      // Create Mock CounterCubit Instance
      final cubit = MockCounterCubit();

      // Stub the listen with a fake Stream
      whenListen(cubit, Stream.fromIterable([1, 2, 3, 4]));

      // Expect that the CounterCubit instance emitted the stubbed Stream of
      // states
      expectLater(cubit.stream, emitsInOrder(<int>[1, 2, 3, 4]));
    });
  });

  group('CounterCubit', () {
    blocTest<CounterCubit, int>(
      'emits [] when nothing is called',
      build: () => CounterCubit(),
      expect: () => const <int>[],
    );

    blocTest<CounterCubit, int>(
      'add \'Fish\' is called',
      build: () => CounterCubit(),
      act: (cubit) => cubit.countUp(),
      expect: () => const <int>[1],
    );

    blocTest<CounterCubit, int>(
      'remove \'Fish\'  is called',
      build: () => CounterCubit(),
      seed: () => 1,
      act: (cubit) => cubit.countDown(),
      expect: () => const <int>[0],
    );
  });
}