236 lines
6.4 KiB
Markdown
236 lines
6.4 KiB
Markdown
---
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id: 5a24c314108439a4d4036144
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title: Use Provider to Connect Redux to React
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challengeType: 6
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isRequired: false
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forumTopicId: 301435
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localeTitle: 使用 Provider 连接 Redux 和 React
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---
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## Description
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<section id='description'>
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在上一挑战中，你创建了 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。<code>react-redux</code>包可帮助我们完成这些任务。
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React Redux 提供的 API 有两个关键的功能：<code>Provider</code>和<code>connect</code>。你会在另一个挑战中学<code>connect</code>。<code>Provider</code>是 React Redux 包装 React 应用的 wrapper 组件，它允许你访问整个组件树中的 Redux<code>store</code>及<code>dispatch（分发）</code>方法。<code>Provider</code>需要两个 props：Redux store 和 APP 应用的子组件。用于 APP 组件的<code>Provider</code>可这样定义：
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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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</section>
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## Instructions
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<section id='instructions'>
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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、<code>DisplayMessages</code>组件。新出现的代码是底部的<code>AppWrapper</code>组件，这个顶级组件可用于渲染<code>ReactRedux</code>的<code>Provider</code>，并把 Redux 的 store 作为 props 传入。接着，渲染<code>DisplayMessages</code>为子组件。完成这些任务后，你会看到 React 组件渲染到页面上。
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<strong>注意：</strong> React Redux 在此可作全局变量，因此你可通过点号表示法访问 Provider。利用这一点，编辑器上的代码把<code>Provider</code>设置为常量，便于你在<code>AppWrapper</code>渲染方法中使用。
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>AppWrapper</code>应渲染。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('AppWrapper').length === 1; })());
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- text: <code>Provider</code>组件应传入相当于 Redux store 的<code>store</code>参数。
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testString: getUserInput => assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return getUserInput('index').replace(/\s/g,'').includes('<Providerstore={store}>'); })());
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- text: <code>DisplayMessages</code>应渲染为<code>AppWrapper</code>的子组件。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('AppWrapper').find('DisplayMessages').length === 1; })());
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- text: <code>DisplayMessages</code>组件应渲染 h2、input、button、<code>ul</code>四个元素。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('div').length === 1 && mockedComponent.find('h2').length === 1 && mockedComponent.find('button').length === 1 && mockedComponent.find('ul').length === 1; })());
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='jsx-seed'>
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```jsx
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// Redux 代码：
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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 代码：
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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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const currentMessage = this.state.input;
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this.setState({
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input: '',
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messages: this.state.messages.concat(currentMessage)
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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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// 在此渲染 Provider
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// 请在本行以上添加你的代码
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};
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```
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</div>
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### After Test
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<div id='jsx-teardown'>
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```js
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ReactDOM.render(<AppWrapper />, document.getElementById('root'))
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// Redux Code:
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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 Code:
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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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const currentMessage = this.state.input;
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this.setState({
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input: '',
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messages: this.state.messages.concat(currentMessage)
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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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</section>
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