157 lines
3.8 KiB
Markdown
157 lines
3.8 KiB
Markdown
---
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id: 5a24c314108439a4d4036147
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title: 連接 Redux 和 React
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challengeType: 6
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forumTopicId: 301426
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dashedName: connect-redux-to-react
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---
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# --description--
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你已經寫了`mapStateToProps()`、`mapDispatchToProps()` 兩個函數，現在可以用它們來把 `state` 和 `dispatch` 映射到 React 組件的 `props` 了。 React Redux 的 `connect` 方法可以完成這個任務。 此方法有 `mapStateToProps()`、`mapDispatchToProps()` 兩個可選參數， 它們是可選的，原因是你的組件可能僅需要訪問 `state` 但不需要分發任何 actions，反之亦然。
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爲了使用此方法，需要傳入函數參數並在調用時傳入組件。 這種語法有些不尋常，如下所示：
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```js
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connect(mapStateToProps, mapDispatchToProps)(MyComponent)
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```
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**注意：**如果要省略 `connect` 方法中的某個參數，則應當用 `null` 替換這個參數。
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# --instructions--
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代碼編輯器具有 `mapStateToProps()` 和 `mapDispatchToProps()` 函數，以及一個名爲 `Presentational` 的新 React 組件。 使用 `ReactRedux` 全局對象中的 `connect` 方法將此組件連接到 Redux，並立即在 `Presentational` 組件上調用它。 將結果賦值給名爲 `ConnectedComponent` 的新 `const`，表示連接的組件。 就是這樣，現在你已經連接到 Redux 了！ 嘗試將 `connect` 的參數更改爲 `null`，並觀察測試結果。
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# --hints--
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應渲染 `Presentational` 組件。
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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('Presentational').length === 1;
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})()
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);
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```
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`Presentational` 組件應通過 `connect` 接收一個 `messages` 屬性。
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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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`Presentational` 組件應通過 `connect` 接收一個 `submitNewMessage` 屬性。
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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 typeof props.submitNewMessage === 'function';
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})()
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);
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```
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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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# --solutions--
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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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