2018-10-10 22:03:03 +00:00
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---
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id: 5a24c314108439a4d4036147
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2020-12-16 07:37:30 +00:00
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title: 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: 301426
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2021-01-13 02:31:00 +00:00
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dashedName: 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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既然写了`mapStateToProps()`、`mapDispatchToProps()`两个函数,现在你可以用它们来把`state`和`dispatch`映射到 React 组件的`props`了。React Redux 的`connect`方法可以完成这个任务。此方法有`mapStateToProps()`、`mapDispatchToProps()`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`状态`但不需要分发任何 actions,反之亦然。
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2020-09-07 08:11:48 +00:00
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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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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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`connect(mapStateToProps, mapDispatchToProps)(MyComponent)`
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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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**注意:** 如果要省略`connect`方法中的某个参数,则应当用`null`替换这个参数。
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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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# --instructions--
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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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在编辑器上有两个函数:`mapStateToProps()`、`mapDispatchToProps()`,还有一个叫`Presentational`的 React 组件。用`ReactRedux`全局对象中的`connect`方法将此组件连接到 Redux,并立即在`Presentational`组件中调用,把结果赋值给一个名为`ConnectedComponent`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`connect`参数为`null`并观察测试结果。
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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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2020-12-16 07:37:30 +00:00
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应渲染`Presentational`组件。
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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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return mockedComponent.find('Presentational').length === 1;
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})()
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2020-09-07 08:11:48 +00:00
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);
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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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`Presentational`组件应通过`connect`接收一个`messages`属性。
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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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const props = mockedComponent.find('Presentational').props();
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return props.messages === '__INITIAL__STATE__';
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})()
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);
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```
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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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`Presentational`组件应通过`connect`接收一个`submitNewMessage`属性。
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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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const props = mockedComponent.find('Presentational').props();
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return typeof props.submitNewMessage === 'function';
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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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2020-08-13 15:24:35 +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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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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## --seed-contents--
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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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// Change code below this line
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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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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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