04-Refactoring_the_Entry_Point.md

04. Refactoring the Entry Point

Video Link

In this lesson we will extract the logic necessary for creating & subscribing to the store into a separate file.

index.js Before

import 'babel-polyfill'
import React from 'react'
import { render } from 'react-dom'
import { Provider } from 'react-redux'
import { createStore } from 'redux'
import throttle from 'lodash/throttle'
import todoApp from './reducers'
import App from './components/App'
import { loadState, saveState } from './localStorage'

const persistedState = loadState()
const store = createStore(
  todoApp,
  persistedState
);

store.subscribe(throttle(() => {
  saveState({
    todos: store.getState().todos,
  })
}, 1000))

render(
  <Provider store={store}>
    <App />
  </Provider>,
  document.getElementById('root')
)

We will call our new file configureStore.js, and start by creating a funcion configureStore that will contain the store creation & persistence logic.

We do this because this way our app doesn't have to know exactly how the store is created and whether or not we have subscribe handlers. It can just use the returned store in the index.js file.

configureStore.js

import { createStore } from 'redux'
import throttle from 'lodash/throttle'
import todoApp from './reducers'
import { loadState, saveState } from './localStorage'

const configureStore = () => {
  const persistedState = loadState()
  const store = createStore(todoApp, persistedState)

  store.subscribe(throttle(() => {
    saveState({
      todos: store.getState().todos
    })
  }, 1000))

  return store
}

export default configureStore

By exporting configureStore instead of just store, we will be able to create as many store instances as we want for testing.

index.js After

import 'babel-polyfill'
import React from 'react'
import { render } from 'react-dom'
import Root from './components/Root'
import configureStore from './configureStore'

const store = configureStore()
render(
  <Root store={store} />,
  document.getElementById('root')
);

Note that we have also extracted the root rendered element into a separate component called Root. It accepts store as a prop, and will be defined in a separate file in our src/components folder.

---

Root Component

import React, { PropTypes } from 'react';
import { Provider } from 'react-redux';
import App from './App';

const Root = ({ store }) => (
  <Provider store={store}>
    <App />
  </Provider>
);

Root.propTypes = {
  store: PropTypes.object.isRequired,
};

export default Root;

We've defined a stateless functional component that just takes the store as a prop and returns <App /> inside of react-redux's Provider.

Now inside of index.js, we can remove our Provider import as well as replacing the App component import with our Root component import.

Recap at 1:45 in video

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