Refactor with-context-api example to use functional components (verce…

…l#9092)

examples/with-context-api/README.md

@@ -43,8 +43,8 @@ This example shows how to use react context api in our app.
 
 It provides an example of using `pages/_app.js` to include the context api provider and then shows how both the `pages/index.js` and `pages/about.js` can both share the same data using the context api consumer.
 
-The `pages/index.js` shows how to, from the home page, increment and decrement the context data by 1 (a hard code value in the context provider itself).
+We start of by creating two contexts. One that actually never changes (`CounterDispatchContext`) and one that changes more often (`CounterStateContext`).
 
-The `pages/about.js` shows how to, from the about page, how to pass an increment value from the about page into the context provider itself.
+The `pages/index.js` shows how to, from the home page, increment and decrement the context data by 1 (a hard code value in the context provider itself).
 
-\*_Based on WesBos example_.
+The `pages/about.js` shows how to pass an increment value from the about page into the context provider itself.

examples/with-context-api/components/Counter.js

@@ -0,0 +1,31 @@
+import React, { useReducer, useContext } from 'react'
+
+const CounterStateContext = React.createContext()
+const CounterDispatchContext = React.createContext()
+
+const reducer = (state, action) => {
+  switch (action.type) {
+    case 'INCREASE':
+      return state + 1
+    case 'DECREASE':
+      return state - 1
+    case 'INCREASE_BY':
+      return state + action.payload
+    default:
+      throw new Error(`Unkown action: ${action.type}`)
+  }
+}
+
+export const CounterProvider = ({ children }) => {
+  const [state, dispatch] = useReducer(reducer, 0)
+  return (
+    <CounterDispatchContext.Provider value={dispatch}>
+      <CounterStateContext.Provider value={state}>
+        {children}
+      </CounterStateContext.Provider>
+    </CounterDispatchContext.Provider>
+  )
+}
+
+export const useCount = () => useContext(CounterStateContext)
+export const useDispatchCount = () => useContext(CounterDispatchContext)

examples/with-context-api/pages/_app.js

@@ -1,12 +1,10 @@
 import App from 'next/app'
-/* First we import our provider */
-import CounterProvider from '../components/CounterProvider'
+import { CounterProvider } from '../components/Counter'
 
 class MyApp extends App {
   render () {
     const { Component, pageProps } = this.props
     return (
-      /* Then we wrap our components with the provider */
       <CounterProvider>
         <Component {...pageProps} />
       </CounterProvider>

examples/with-context-api/pages/about.js

@@ -1,33 +1,34 @@
-import React, { Component } from 'react'
-/* First we import the consumer */
-import { CounterConsumer } from '../components/CounterProvider'
+import React from 'react'
 import Link from 'next/link'
+import { useCount, useDispatchCount } from '../components/Counter'
 
-export default class about extends Component {
-  render () {
-    return (
-      /* Then we use our context through render props */
-      <CounterConsumer>
-        {({ count, increase, increaseBy }) => (
-          <div>
-            <h1>ABOUT</h1>
-            <p>Counter: {count}</p>
-            <button onClick={increase}>Increase</button>
-            <button
-              onClick={() => {
-                increaseBy(15)
-              }}
-            >
-              Increase By 15
-            </button>
-            <p>
-              <Link href='/'>
-                <a>Home</a>
-              </Link>
-            </p>
-          </div>
-        )}
-      </CounterConsumer>
-    )
-  }
+const AboutPage = () => {
+  const count = useCount()
+  const dispatch = useDispatchCount()
+
+  const handleIncrease = event =>
+    dispatch({
+      type: 'INCREASE'
+    })
+  const handleIncrease15 = event =>
+    dispatch({
+      type: 'INCREASE_BY',
+      payload: 15
+    })
+
+  return (
+    <>
+      <h1>ABOUT</h1>
+      <p>Counter: {count}</p>
+      <button onClick={handleIncrease}>Increase</button>
+      <button onClick={handleIncrease15}>Increase By 15</button>
+      <p>
+        <Link href='/'>
+          <a>Home</a>
+        </Link>
+      </p>
+    </>
+  )
 }
+
+export default AboutPage

examples/with-context-api/pages/index.js

@@ -1,27 +1,33 @@
-import React, { Component } from 'react'
+import React from 'react'
 import Link from 'next/link'
-/* First we import the consumer */
-import { CounterConsumer } from '../components/CounterProvider'
+import { useCount, useDispatchCount } from '../components/Counter'
 
-export default class index extends Component {
-  render () {
-    return (
-      /* Then we use our context through render props */
-      <CounterConsumer>
-        {({ count, increase, decrease }) => (
-          <div>
-            <h1>HOME</h1>
-            <p>Counter: {count}</p>
-            <button onClick={increase}>Increase</button>
-            <button onClick={decrease}>Decrease</button>
-            <p>
-              <Link href='/about'>
-                <a>About</a>
-              </Link>
-            </p>
-          </div>
-        )}
-      </CounterConsumer>
-    )
-  }
+const IndexPage = () => {
+  const count = useCount()
+  const dispatch = useDispatchCount()
+
+  const handleIncrease = event =>
+    dispatch({
+      type: 'INCREASE'
+    })
+  const handleDecrease = event =>
+    dispatch({
+      type: 'DECREASE'
+    })
+
+  return (
+    <>
+      <h1>HOME</h1>
+      <p>Counter: {count}</p>
+      <button onClick={handleIncrease}>Increase</button>
+      <button onClick={handleDecrease}>Decrease</button>
+      <p>
+        <Link href='/about'>
+          <a>About</a>
+        </Link>
+      </p>
+    </>
+  )
 }
+
+export default IndexPage