148 lines
4.3 KiB
Markdown
148 lines
4.3 KiB
Markdown
---
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id: 5a24c314108439a4d4036147
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challengeType: 6
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forumTopicId: 301426
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title: 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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既然写了<code>mapStateToProps()</code>、<code>mapDispatchToProps()</code>两个函数，现在你可以用它们来把<code>state</code>和<code>dispatch</code>映射到 React 组件的<code>props</code>了。React Redux 的<code>connect</code>方法可以完成这个任务。此方法有<code>mapStateToProps()</code>、<code>mapDispatchToProps()</code>两个可选参数，它们是可选的，原因是你的组件可能仅需要访问<code>状态</code>但不需要分发任何 actions，反之亦然。
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为了使用此方法，需要传入函数参数并在调用时传入组件。这种语法有些不寻常，如下所示：
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<code>connect(mapStateToProps, mapDispatchToProps)(MyComponent)</code>
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<strong>注意：</strong> 如果要省略<code>connect</code>方法中的某个参数，则应当用<code>null</code>替换这个参数。
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</section>
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## Instructions
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<section id='instructions'>
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在编辑器上有两个函数：<code>mapStateToProps()</code>、<code>mapDispatchToProps()</code>，还有一个叫<code>Presentational</code>的 React 组件。用<code>ReactRedux</code>全局对象中的<code>connect</code>方法将此组件连接到 Redux，并立即在<code>Presentational</code>组件中调用，把结果赋值给一个名为<code>ConnectedComponent</code>的代表已连接组件的新常量。大功告成！你已成功把 React 连接到 Redux！尝试更改任何一个<code>connect</code>参数为<code>null</code>并观察测试结果。
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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: 应渲染<code>Presentational</code>组件。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('Presentational').length === 1; })());
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- text: <code>Presentational</code>组件应通过<code>connect</code>接收一个<code>messages</code>属性。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); const props = mockedComponent.find('Presentational').props(); return props.messages === '__INITIAL__STATE__'; })());
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- text: <code>Presentational</code>组件应通过<code>connect</code>接收一个<code>submitNewMessage</code>属性。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); const props = mockedComponent.find('Presentational').props(); return typeof props.submitNewMessage === 'function'; })());
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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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const addMessage = (message) => {
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return {
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type: 'ADD',
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message: message
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}
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};
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const mapStateToProps = (state) => {
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return {
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messages: state
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}
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};
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const mapDispatchToProps = (dispatch) => {
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return {
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submitNewMessage: (message) => {
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dispatch(addMessage(message));
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}
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}
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};
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class Presentational extends React.Component {
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constructor(props) {
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super(props);
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}
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render() {
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return <h3>This is a Presentational Component</h3>
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}
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};
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const connect = ReactRedux.connect;
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// 请在本行以下添加你的代码
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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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const store = Redux.createStore(
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(state = '__INITIAL__STATE__', action) => state
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);
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class AppWrapper extends React.Component {
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render() {
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return (
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<ReactRedux.Provider store = {store}>
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<ConnectedComponent/>
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</ReactRedux.Provider>
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);
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}
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};
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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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const addMessage = (message) => {
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return {
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type: 'ADD',
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message: message
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}
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};
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const mapStateToProps = (state) => {
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return {
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messages: state
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}
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};
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const mapDispatchToProps = (dispatch) => {
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return {
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submitNewMessage: (message) => {
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dispatch(addMessage(message));
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}
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}
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};
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class Presentational extends React.Component {
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constructor(props) {
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super(props);
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}
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render() {
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return <h3>This is a Presentational Component</h3>
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}
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};
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const connect = ReactRedux.connect;
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// change code below this line
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const ConnectedComponent = connect(mapStateToProps, mapDispatchToProps)(Presentational);
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```
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</section>
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