ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
153 lines
3.7 KiB
Markdown
153 lines
3.7 KiB
Markdown
---
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id: 5a24c314108439a4d4036151
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title: 使用 Switch 语句处理多个 Actions
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challengeType: 6
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forumTopicId: 301449
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dashedName: use-a-switch-statement-to-handle-multiple-actions
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---
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# --description--
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你可以定义 Redux store 如何处理多种 action 类型。比如你正在 Redux store 中进行用户身份验证，如果你希望用户在登录和注销时具有状态的响应，你可以使用具有`authenticated`属性的单个的 state 对象。你还需要使用 action creators 创建与用户登录和用户注销相对应的 action，以及 action 对象本身。
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# --instructions--
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代码编辑器为你创建了 store、actions、action creators。通过编写`reducer`函数来处理多个身份验证操作。可以在`reducer`通过使用 JavaScript 的`switch`来响应不同的 action 事件。这是编写 Redux reducer 时的标准模式，switch 语句选择`action.type`中的一个值并返回相应的身份验证状态。
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**注意：** 此时，不要担心 state 的不变性，因为在这个示例中它很小而且很简单。所以对于每个操作你都可以返回一个新对象，比如`{authenticated:true}`。另外，不要忘记在 switch 语句中写一个`default` case，返回当前的`state`。这是很重要的，因为一旦你的程序有多个 reducer，当一个 action 被 dispatch 时它们都会运行，即使 action 与该 reducer 无关。在这种情况下，你要确保返回当前的`state`
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# --hints--
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调用`loginUser`函数应该返回一个 {type:"LOGIN"} 对象。
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```js
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assert(loginUser().type === 'LOGIN');
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```
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调用`logoutUser`函数应该返回一个 {type:"LOGOUT"} 对象。
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```js
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assert(logoutUser().type === 'LOGOUT');
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```
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store 应该设置一个初始化对象 {authenticated:false}。
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```js
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assert(store.getState().authenticated === false);
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```
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dispatch `loginUser`应该将 store 中的 state 的`authenticated`值更新为`true`。
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```js
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assert(
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(function () {
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const initialState = store.getState();
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store.dispatch(loginUser());
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const afterLogin = store.getState();
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return (
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initialState.authenticated === false && afterLogin.authenticated === true
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);
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})()
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);
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```
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dispatch `logoutUser`应该将 store 中的 state 的`authenticated`值更新为`false`。
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```js
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assert(
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(function () {
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store.dispatch(loginUser());
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const loggedIn = store.getState();
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store.dispatch(logoutUser());
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const afterLogout = store.getState();
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return (
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loggedIn.authenticated === true && afterLogout.authenticated === false
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);
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})()
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);
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```
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`authReducer`函数应该使用`switch`语句处理多个 action 类型。
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```js
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(getUserInput) =>
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assert(
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getUserInput('index').toString().includes('switch') &&
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getUserInput('index').toString().includes('case') &&
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getUserInput('index').toString().includes('default')
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);
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```
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# --seed--
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## --seed-contents--
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```js
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const defaultState = {
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authenticated: false
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};
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const authReducer = (state = defaultState, action) => {
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// Change code below this line
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// Change code above this line
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};
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const store = Redux.createStore(authReducer);
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const loginUser = () => {
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return {
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type: 'LOGIN'
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}
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};
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const logoutUser = () => {
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return {
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type: 'LOGOUT'
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}
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};
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```
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# --solutions--
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```js
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const defaultState = {
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authenticated: false
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};
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const authReducer = (state = defaultState, action) => {
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switch (action.type) {
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case 'LOGIN':
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return {
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authenticated: true
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}
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case 'LOGOUT':
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return {
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authenticated: false
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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(authReducer);
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const loginUser = () => {
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return {
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type: 'LOGIN'
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}
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};
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const logoutUser = () => {
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return {
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type: 'LOGOUT'
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}
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};
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```
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