2018-10-10 22:03:03 +00:00
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---
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id: 5a24c314108439a4d4036144
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2021-03-05 15:43:24 +00:00
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title: 使用 Provider 连接 Redux 和 React
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2018-10-10 22:03:03 +00:00
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challengeType: 6
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2020-09-07 08:11:48 +00:00
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forumTopicId: 301435
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2021-01-13 02:31:00 +00:00
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dashedName: use-provider-to-connect-redux-to-react
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2018-10-10 22:03:03 +00:00
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2021-03-05 15:43:24 +00:00
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在上一挑战中,创建了 Redux store 和 action,分别用于处理消息数组和添加新消息。 下一步要为 React 提供访问 Redux store 及发起更新所需的 actions。 `react-redux` 包可帮助我们完成这些任务。
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2020-12-16 07:37:30 +00:00
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2021-03-05 15:43:24 +00:00
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React Redux 提供的 API 有两个关键的功能:`Provider` 和 `connect`。 会在另一个挑战会介绍 `connect`。 `Provider`是 React Redux 包装 React 应用的 wrapper 组件, 它允许访问整个组件树中的 Redux `store` 及 `dispatch`(分发)方法。 `Provider` 需要两个 props:Redux store 和 App 应用的子组件。 用于 App 组件的 `Provider` 可这样定义:
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2020-09-07 08:11:48 +00:00
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```jsx
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<Provider store={store}>
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<App/>
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</Provider>
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```
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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此时,编辑器上显示的是过去几个挑战中所有代码, 包括 Redux store、actions、`DisplayMessages` 组件。 新出现的代码是底部的`AppWrapper`组件, 这个顶级组件可用于渲染 `ReactRedux` 的 `Provider`,并把 Redux 的 store 作为 props 传入。 接着,渲染 `DisplayMessages` 为子组件。 完成这些任务后,会看到 React 组件渲染到页面上。
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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**注意:** React Redux 在此可作全局变量,因此可通过点号表示法访问 Provider。 利用这一点,编辑器上的代码把 `Provider` 设置为常量,便于你在 `AppWrapper` 渲染方法中使用。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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`AppWrapper` 应渲染。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
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return mockedComponent.find('AppWrapper').length === 1;
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2021-03-05 15:43:24 +00:00
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`Provider` 组件应传入相当于 Redux store 的 `store` 参数。
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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(getUserInput) =>
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
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2021-02-06 04:42:36 +00:00
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return __helpers
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.removeWhiteSpace(getUserInput('index'))
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2020-12-16 07:37:30 +00:00
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.includes('<Providerstore={store}>');
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2021-03-05 15:43:24 +00:00
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`DisplayMessages` 应渲染为 `AppWrapper` 的子组件。
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2020-09-07 08:11:48 +00:00
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
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2020-09-07 08:11:48 +00:00
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return (
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2020-12-16 07:37:30 +00:00
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mockedComponent.find('AppWrapper').find('DisplayMessages').length === 1
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2020-09-07 08:11:48 +00:00
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);
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2020-12-16 07:37:30 +00:00
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})()
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);
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```
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2020-08-13 15:24:35 +00:00
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2021-03-05 15:43:24 +00:00
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`DisplayMessages` 组件应渲染 `h2`、`input`、`button`、`ul` 四个元素。
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2020-09-07 08:11:48 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
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2020-09-07 08:11:48 +00:00
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return (
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2020-12-16 07:37:30 +00:00
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mockedComponent.find('div').length === 1 &&
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mockedComponent.find('h2').length === 1 &&
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mockedComponent.find('button').length === 1 &&
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mockedComponent.find('ul').length === 1
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2020-09-07 08:11:48 +00:00
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);
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2020-12-16 07:37:30 +00:00
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})()
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);
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2020-09-07 08:11:48 +00:00
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```
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2020-12-16 07:37:30 +00:00
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2021-01-13 02:31:00 +00:00
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# --seed--
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## --after-user-code--
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```jsx
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ReactDOM.render(<AppWrapper />, document.getElementById('root'))
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```
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## --seed-contents--
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```jsx
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// Redux:
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const ADD = 'ADD';
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const addMessage = (message) => {
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return {
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type: ADD,
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message
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}
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};
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const messageReducer = (state = [], action) => {
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switch (action.type) {
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case ADD:
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return [
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...state,
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action.message
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];
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default:
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return state;
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}
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};
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const store = Redux.createStore(messageReducer);
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// React:
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class DisplayMessages extends React.Component {
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constructor(props) {
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super(props);
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this.state = {
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input: '',
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messages: []
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}
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this.handleChange = this.handleChange.bind(this);
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this.submitMessage = this.submitMessage.bind(this);
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}
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handleChange(event) {
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this.setState({
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input: event.target.value
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});
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}
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submitMessage() {
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this.setState((state) => {
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const currentMessage = state.input;
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return {
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input: '',
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messages: state.messages.concat(currentMessage)
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};
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});
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}
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render() {
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return (
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<div>
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<h2>Type in a new Message:</h2>
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<input
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value={this.state.input}
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onChange={this.handleChange}/><br/>
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<button onClick={this.submitMessage}>Submit</button>
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<ul>
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{this.state.messages.map( (message, idx) => {
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return (
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<li key={idx}>{message}</li>
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)
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})
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}
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</ul>
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</div>
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);
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}
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};
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const Provider = ReactRedux.Provider;
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class AppWrapper extends React.Component {
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// Render the Provider below this line
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// Change code above this line
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};
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```
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2020-12-16 07:37:30 +00:00
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# --solutions--
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2021-01-13 02:31:00 +00:00
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```jsx
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// Redux:
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const ADD = 'ADD';
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const addMessage = (message) => {
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return {
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type: ADD,
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message
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}
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};
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const messageReducer = (state = [], action) => {
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switch (action.type) {
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case ADD:
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return [
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...state,
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action.message
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];
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default:
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return state;
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}
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};
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const store = Redux.createStore(messageReducer);
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// React:
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class DisplayMessages extends React.Component {
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constructor(props) {
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super(props);
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this.state = {
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input: '',
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messages: []
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}
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this.handleChange = this.handleChange.bind(this);
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this.submitMessage = this.submitMessage.bind(this);
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}
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handleChange(event) {
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this.setState({
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input: event.target.value
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});
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}
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submitMessage() {
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this.setState((state) => {
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const currentMessage = state.input;
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return {
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input: '',
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messages: state.messages.concat(currentMessage)
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};
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});
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}
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render() {
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return (
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<div>
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<h2>Type in a new Message:</h2>
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<input
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value={this.state.input}
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onChange={this.handleChange}/><br/>
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<button onClick={this.submitMessage}>Submit</button>
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<ul>
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{this.state.messages.map( (message, idx) => {
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return (
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<li key={idx}>{message}</li>
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)
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})
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}
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</ul>
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</div>
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);
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}
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};
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const Provider = ReactRedux.Provider;
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class AppWrapper extends React.Component {
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// Change code below this line
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render() {
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return (
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<Provider store = {store}>
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<DisplayMessages/>
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</Provider>
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);
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}
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// Change code above this line
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};
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```
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