From 12791c44293e6788452124f4fba67611b62d537f Mon Sep 17 00:00:00 2001
From: handtrix <handtrix@gmail.com>
Date: Fri, 27 Sep 2019 11:22:54 +0200
Subject: [PATCH] Simplify with-redux example

## Changes

- [x] Remove _app.js usage
- [x] Migrate withRedux HOC to functional component
- [x] Add correct display name
- [x] Remove abstractions/boilerplate from example
- [x] Add useInterval HOC from Dan
---
 examples/with-redux/README.md               |  9 +--
 examples/with-redux/components/clock.js     | 25 ++++++-
 examples/with-redux/components/counter.js   | 33 +++++-----
 examples/with-redux/components/examples.js  | 20 ------
 examples/with-redux/lib/redux.js            | 72 +++++++++++++++++++++
 examples/with-redux/lib/useInterval.js      | 19 ++++++
 examples/with-redux/lib/with-redux-store.js | 50 --------------
 examples/with-redux/package.json            |  4 +-
 examples/with-redux/pages/_app.js           | 17 -----
 examples/with-redux/pages/index.js          | 62 ++++++++++--------
 examples/with-redux/store.js                | 68 +++++++------------
 11 files changed, 190 insertions(+), 189 deletions(-)
 delete mode 100644 examples/with-redux/components/examples.js
 create mode 100644 examples/with-redux/lib/redux.js
 create mode 100644 examples/with-redux/lib/useInterval.js
 delete mode 100644 examples/with-redux/lib/with-redux-store.js
 delete mode 100644 examples/with-redux/pages/_app.js

diff --git a/examples/with-redux/README.md b/examples/with-redux/README.md
index 68d6cf5971602..df7ceff24d998 100644
--- a/examples/with-redux/README.md
+++ b/examples/with-redux/README.md
@@ -45,13 +45,10 @@ Usually splitting your app state into `pages` feels natural but sometimes you'll
 
 In the first example we are going to display a digital clock that updates every second. The first render is happening in the server and then the browser will take over. To illustrate this, the server rendered clock will have a different background color (black) than the client one (grey).
 
-The Redux `Provider` is implemented in `pages/_app.js`. Since the `MyApp` component is wrapped in `withReduxStore` the redux store will be automatically initialized and provided to `MyApp`, which in turn passes it off to `react-redux`'s `Provider` component.
+The Redux `Provider` is implemented in `lib/redux.js`. Since the `IndexPage` component is wrapped in `withRedux` the redux context will be automatically initialized and provided to `IndexPage`.
 
-`index.js` have access to the redux store using `connect` from `react-redux`.
-`counter.js` and `examples.js` have access to the redux store using `useSelector` and `useDispatch` from `react-redux@^7.1.0`
+All components have access to the redux store using `useSelector`, `useDispatch` or `connect` from `react-redux`.
 
 On the server side every request initializes a new store, because otherwise different user data can be mixed up. On the client side the same store is used, even between page changes.
 
-The example under `components/counter.js`, shows a simple incremental counter implementing a common Redux pattern of mapping state to props. Again, the first render is happening in the server and instead of starting the count at 0, it will dispatch an action in redux that starts the count at 1. This continues to highlight how each navigation triggers a server render first and then a client render when switching pages on the client side
-
-For simplicity and readability, Reducers, Actions, and Store creators are all in the same file: `store.js`
+The example under `components/counter.js`, shows a simple incremental counter implementing a common Redux pattern of mapping state to props. Again, the first render is happening in the server and instead of starting the count at 0, it will dispatch an action in redux that starts the count at 1. This continues to highlight how each navigation triggers a server render first and then a client render when switching pages on the client side.
diff --git a/examples/with-redux/components/clock.js b/examples/with-redux/components/clock.js
index 4e71fc3a92f96..7d9de8ad1a8a2 100644
--- a/examples/with-redux/components/clock.js
+++ b/examples/with-redux/components/clock.js
@@ -1,7 +1,26 @@
-export default ({ lastUpdate, light }) => {
+import React from 'react'
+import { useSelector, shallowEqual } from 'react-redux'
+
+const useClock = () => {
+  return useSelector(
+    state => ({
+      lastUpdate: state.lastUpdate,
+      light: state.light
+    }),
+    shallowEqual
+  )
+}
+
+const formatTime = time => {
+  // cut off except hh:mm:ss
+  return new Date(time).toJSON().slice(11, 19)
+}
+
+const Clock = () => {
+  const { lastUpdate, light } = useClock()
   return (
     <div className={light ? 'light' : ''}>
-      {format(new Date(lastUpdate))}
+      {formatTime(lastUpdate)}
       <style jsx>{`
         div {
           padding: 15px;
@@ -19,4 +38,4 @@ export default ({ lastUpdate, light }) => {
   )
 }
 
-const format = t => t.toJSON().slice(11, 19) // cut off except hh:mm:ss
+export default Clock
diff --git a/examples/with-redux/components/counter.js b/examples/with-redux/components/counter.js
index 5ce890bfc27b2..ebbbc64e13b1b 100644
--- a/examples/with-redux/components/counter.js
+++ b/examples/with-redux/components/counter.js
@@ -1,27 +1,26 @@
 import React from 'react'
 import { useSelector, useDispatch } from 'react-redux'
-import { incrementCount, decrementCount, resetCount } from '../store'
-
-const countSelector = state => state.count
 
 const useCounter = () => {
+  const count = useSelector(state => state.count)
   const dispatch = useDispatch()
-  const increment = () => {
-    dispatch(incrementCount())
-  }
-  const decrement = () => {
-    dispatch(decrementCount())
-  }
-  const reset = () => {
-    dispatch(resetCount())
-  }
-
-  return { increment, decrement, reset }
+  const increment = () =>
+    dispatch({
+      type: 'INCREMENT'
+    })
+  const decrement = () =>
+    dispatch({
+      type: 'DECREMENT'
+    })
+  const reset = () =>
+    dispatch({
+      type: 'RESET'
+    })
+  return { count, increment, decrement, reset }
 }
 
-function Counter () {
-  const count = useSelector(countSelector)
-  const { increment, decrement, reset } = useCounter()
+const Counter = () => {
+  const { count, increment, decrement, reset } = useCounter()
   return (
     <div>
       <h1>
diff --git a/examples/with-redux/components/examples.js b/examples/with-redux/components/examples.js
deleted file mode 100644
index 9cbe45e470123..0000000000000
--- a/examples/with-redux/components/examples.js
+++ /dev/null
@@ -1,20 +0,0 @@
-import { useSelector, shallowEqual } from 'react-redux'
-import Clock from './clock'
-import Counter from './counter'
-
-const clockSelector = state => ({
-  lastUpdate: state.lastUpdate,
-  light: state.light
-})
-
-function Examples () {
-  const { lastUpdate, light } = useSelector(clockSelector, shallowEqual)
-  return (
-    <div>
-      <Clock lastUpdate={lastUpdate} light={light} />
-      <Counter />
-    </div>
-  )
-}
-
-export default Examples
diff --git a/examples/with-redux/lib/redux.js b/examples/with-redux/lib/redux.js
new file mode 100644
index 0000000000000..721e44ef34a78
--- /dev/null
+++ b/examples/with-redux/lib/redux.js
@@ -0,0 +1,72 @@
+import React from 'react'
+import { Provider } from 'react-redux'
+import { initializeStore } from '../store'
+import App from 'next/app'
+
+export const withRedux = (PageComponent, { ssr = true } = {}) => {
+  const WithRedux = ({ initialReduxState, ...props }) => {
+    const store = getOrInitializeStore(initialReduxState)
+    return (
+      <Provider store={store}>
+        <PageComponent {...props} />
+      </Provider>
+    )
+  }
+
+  // Make sure people don't use this HOC on _app.js level
+  if (process.env.NODE_ENV !== 'production') {
+    const isAppHoc =
+      PageComponent === App || PageComponent.prototype instanceof App
+    if (isAppHoc) {
+      throw new Error('The withRedux HOC only works with PageComponents')
+    }
+  }
+
+  // Set the correct displayName in development
+  if (process.env.NODE_ENV !== 'production') {
+    const displayName =
+      PageComponent.displayName || PageComponent.name || 'Component'
+
+    WithRedux.displayName = `withRedux(${displayName})`
+  }
+
+  if (ssr || PageComponent.getInitialProps) {
+    WithRedux.getInitialProps = async context => {
+      // Get or Create the store with `undefined` as initialState
+      // This allows you to set a custom default initialState
+      const reduxStore = getOrInitializeStore()
+
+      // Provide the store to getInitialProps of pages
+      context.reduxStore = reduxStore
+
+      // Run getInitialProps from HOCed PageComponent
+      const pageProps =
+        typeof PageComponent.getInitialProps === 'function'
+          ? await PageComponent.getInitialProps(context)
+          : {}
+
+      // Pass props to PageComponent
+      return {
+        ...pageProps,
+        initialReduxState: reduxStore.getState()
+      }
+    }
+  }
+
+  return WithRedux
+}
+
+let reduxStore
+const getOrInitializeStore = initialState => {
+  // Always make a new store if server, otherwise state is shared between requests
+  if (typeof window === 'undefined') {
+    return initializeStore(initialState)
+  }
+
+  // Create store if unavailable on the client and set it on the window object
+  if (!reduxStore) {
+    reduxStore = initializeStore(initialState)
+  }
+
+  return reduxStore
+}
diff --git a/examples/with-redux/lib/useInterval.js b/examples/with-redux/lib/useInterval.js
new file mode 100644
index 0000000000000..066d08ee254b5
--- /dev/null
+++ b/examples/with-redux/lib/useInterval.js
@@ -0,0 +1,19 @@
+import { useEffect, useRef } from 'react'
+
+// https://overreacted.io/making-setinterval-declarative-with-react-hooks/
+const useInterval = (callback, delay) => {
+  const savedCallback = useRef()
+  useEffect(() => {
+    savedCallback.current = callback
+  }, [callback])
+  useEffect(() => {
+    const handler = (...args) => savedCallback.current(...args)
+
+    if (delay !== null) {
+      const id = setInterval(handler, delay)
+      return () => clearInterval(id)
+    }
+  }, [delay])
+}
+
+export default useInterval
diff --git a/examples/with-redux/lib/with-redux-store.js b/examples/with-redux/lib/with-redux-store.js
deleted file mode 100644
index b6369a517bd16..0000000000000
--- a/examples/with-redux/lib/with-redux-store.js
+++ /dev/null
@@ -1,50 +0,0 @@
-import React from 'react'
-import { initializeStore } from '../store'
-
-const isServer = typeof window === 'undefined'
-const __NEXT_REDUX_STORE__ = '__NEXT_REDUX_STORE__'
-
-function getOrCreateStore (initialState) {
-  // Always make a new store if server, otherwise state is shared between requests
-  if (isServer) {
-    return initializeStore(initialState)
-  }
-
-  // Create store if unavailable on the client and set it on the window object
-  if (!window[__NEXT_REDUX_STORE__]) {
-    window[__NEXT_REDUX_STORE__] = initializeStore(initialState)
-  }
-  return window[__NEXT_REDUX_STORE__]
-}
-
-export default App => {
-  return class AppWithRedux extends React.Component {
-    static async getInitialProps (appContext) {
-      // Get or Create the store with `undefined` as initialState
-      // This allows you to set a custom default initialState
-      const reduxStore = getOrCreateStore()
-
-      // Provide the store to getInitialProps of pages
-      appContext.ctx.reduxStore = reduxStore
-
-      let appProps = {}
-      if (typeof App.getInitialProps === 'function') {
-        appProps = await App.getInitialProps(appContext)
-      }
-
-      return {
-        ...appProps,
-        initialReduxState: reduxStore.getState()
-      }
-    }
-
-    constructor (props) {
-      super(props)
-      this.reduxStore = getOrCreateStore(props.initialReduxState)
-    }
-
-    render () {
-      return <App {...this.props} reduxStore={this.reduxStore} />
-    }
-  }
-}
diff --git a/examples/with-redux/package.json b/examples/with-redux/package.json
index ca6d032c27d19..04c01fe8efb4d 100644
--- a/examples/with-redux/package.json
+++ b/examples/with-redux/package.json
@@ -9,10 +9,10 @@
   "dependencies": {
     "next": "latest",
     "react": "^16.9.0",
-    "redux-devtools-extension": "^2.13.2",
     "react-dom": "^16.9.0",
     "react-redux": "^7.1.0",
-    "redux": "^3.6.0"
+    "redux": "^3.6.0",
+    "redux-devtools-extension": "^2.13.2"
   },
   "license": "ISC"
 }
diff --git a/examples/with-redux/pages/_app.js b/examples/with-redux/pages/_app.js
deleted file mode 100644
index 5f4467a9dad5e..0000000000000
--- a/examples/with-redux/pages/_app.js
+++ /dev/null
@@ -1,17 +0,0 @@
-import App from 'next/app'
-import React from 'react'
-import withReduxStore from '../lib/with-redux-store'
-import { Provider } from 'react-redux'
-
-class MyApp extends App {
-  render () {
-    const { Component, pageProps, reduxStore } = this.props
-    return (
-      <Provider store={reduxStore}>
-        <Component {...pageProps} />
-      </Provider>
-    )
-  }
-}
-
-export default withReduxStore(MyApp)
diff --git a/examples/with-redux/pages/index.js b/examples/with-redux/pages/index.js
index 1500af6301101..15c72e95b6535 100644
--- a/examples/with-redux/pages/index.js
+++ b/examples/with-redux/pages/index.js
@@ -1,33 +1,39 @@
 import React from 'react'
-import { connect } from 'react-redux'
-import { startClock, serverRenderClock } from '../store'
-import Examples from '../components/examples'
+import { useDispatch } from 'react-redux'
+import { withRedux } from '../lib/redux'
+import useInterval from '../lib/useInterval'
+import Clock from '../components/clock'
+import Counter from '../components/counter'
 
-class Index extends React.Component {
-  static getInitialProps ({ reduxStore, req }) {
-    const isServer = !!req
-    // DISPATCH ACTIONS HERE ONLY WITH `reduxStore.dispatch`
-    reduxStore.dispatch(serverRenderClock(isServer))
-
-    return {}
-  }
-
-  componentDidMount () {
-    // DISPATCH ACTIONS HERE FROM `mapDispatchToProps`
-    // TO TICK THE CLOCK
-    this.timer = setInterval(() => this.props.startClock(), 1000)
-  }
+const IndexPage = () => {
+  // Tick the time every second
+  const dispatch = useDispatch()
+  useInterval(() => {
+    dispatch({
+      type: 'TICK',
+      light: true,
+      lastUpdate: Date.now()
+    })
+  }, 1000)
+  return (
+    <>
+      <Clock />
+      <Counter />
+    </>
+  )
+}
 
-  componentWillUnmount () {
-    clearInterval(this.timer)
-  }
+IndexPage.getInitialProps = ({ reduxStore }) => {
+  // Tick the time once, so we'll have a
+  // valid time before first render
+  const { dispatch } = reduxStore
+  dispatch({
+    type: 'TICK',
+    light: typeof window === 'object',
+    lastUpdate: Date.now()
+  })
 
-  render () {
-    return <Examples />
-  }
+  return {}
 }
-const mapDispatchToProps = { startClock }
-export default connect(
-  null,
-  mapDispatchToProps
-)(Index)
+
+export default withRedux(IndexPage)
diff --git a/examples/with-redux/store.js b/examples/with-redux/store.js
index 3de7e5db3f0b0..9cdf40df31794 100644
--- a/examples/with-redux/store.js
+++ b/examples/with-redux/store.js
@@ -1,68 +1,44 @@
 import { createStore, applyMiddleware } from 'redux'
 import { composeWithDevTools } from 'redux-devtools-extension'
 
-const exampleInitialState = {
+const initialState = {
   lastUpdate: 0,
   light: false,
   count: 0
 }
 
-export const actionTypes = {
-  TICK: 'TICK',
-  INCREMENT: 'INCREMENT',
-  DECREMENT: 'DECREMENT',
-  RESET: 'RESET'
-}
-
-// REDUCERS
-export const reducer = (state = exampleInitialState, action) => {
+const reducer = (state = initialState, action) => {
   switch (action.type) {
-    case actionTypes.TICK:
-      return Object.assign({}, state, {
-        lastUpdate: action.ts,
+    case 'TICK':
+      return {
+        ...state,
+        lastUpdate: action.lastUpdate,
         light: !!action.light
-      })
-    case actionTypes.INCREMENT:
-      return Object.assign({}, state, {
+      }
+    case 'INCREMENT':
+      return {
+        ...state,
         count: state.count + 1
-      })
-    case actionTypes.DECREMENT:
-      return Object.assign({}, state, {
+      }
+    case 'DECREMENT':
+      return {
+        ...state,
         count: state.count - 1
-      })
-    case actionTypes.RESET:
-      return Object.assign({}, state, {
-        count: exampleInitialState.count
-      })
+      }
+    case 'RESET':
+      return {
+        ...state,
+        count: initialState.count
+      }
     default:
       return state
   }
 }
 
-// ACTIONS
-export const serverRenderClock = () => {
-  return { type: actionTypes.TICK, light: false, ts: Date.now() }
-}
-export const startClock = () => {
-  return { type: actionTypes.TICK, light: true, ts: Date.now() }
-}
-
-export const incrementCount = () => {
-  return { type: actionTypes.INCREMENT }
-}
-
-export const decrementCount = () => {
-  return { type: actionTypes.DECREMENT }
-}
-
-export const resetCount = () => {
-  return { type: actionTypes.RESET }
-}
-
-export function initializeStore (initialState = exampleInitialState) {
+export const initializeStore = (preloadedState = initialState) => {
   return createStore(
     reducer,
-    initialState,
+    preloadedState,
     composeWithDevTools(applyMiddleware())
   )
 }