createReducerを使用したReducerの書き方 - パート1

configureStore.jsx(変更なし)

import { createStore } from 'redux';
import rootReducer from '../reducers';

export default function configureStore(initialState) {
  const store = createStore(
    rootReducer,
    initialState,
  );
  return store;
}

counter.jsx

import * as types from '../constants/ActionTypes';
import { createReducer } from '../modules/helpers';

const initialState = {
  value: 0,
};

export default {
  counter: createReducer(initialState, {
    [types.INCREMENT](state) {
      return Object.assign({}, state, {value: state.value + 1});
    },
    [types.DECREMENT](state) {
      return Object.assign({}, state, {value: state.value - 1});
    },
  }),
};

index.jsx

import { combineReducers } from 'redux';
import counter from './counter';

const rootReducer = combineReducers({
  ...counter, // スプレッド構文使用
});

export default rootReducer;