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

@@ -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.

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

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>

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
+}

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

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"
 }

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)