177 lines
6.0 KiB
Markdown
177 lines
6.0 KiB
Markdown
---
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id: 5a24c314108439a4d403617b
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challengeType: 6
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forumTopicId: 301400
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title: 传递回调作为 Props
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---
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## Description
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<section id='description'>
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你可以将<code>state</code>作为 props 传递给子组件，但不仅限于传递数据。你也可以将处理函数或在 React 组件中定义的任何方法传递给子组件。这就是允许子组件与父组件交互的方式。你可以把方法像普通 prop 一样传递给子组件，它会被分配一个名字，你可以在子组件中的<code>this.props</code>下访问该方法的名字。
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</section>
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## Instructions
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<section id='instructions'>
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代码编辑器中列出了三个组件。<code>MyApp</code>是父组件，<code>GetInput</code>和<code>RenderInput</code>是它的子组件。将<code>GetInput</code>组件添加到<code>MyApp</code>的 render 方法，然后将<code>MyApp</code>的<code>state</code>中的<code>inputValue</code>传入名为<code>input</code>的 prop。还要创建一个名为<code>handleChange</code>的 prop，并将输入处理程序<code>handleChange</code>传递给它。
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接下来，将<code>RenderInput</code>添加到<code>MyApp</code>中的 render 方法中，然后创建一个名为<code>input</code>的 prop，并将<code>state</code>中的<code>inputValue</code>传递给它。完成后，你将能够在<code>GetInput</code>组件中的<code>input</code>字段中键入内容，然后该组件通过 props 调用其父组件中的处理函数方法。这将更新处于父组件<code>state</code>中的 input，该 input 将作为 props 传递给两个子组件。观察数据如何在组件之间流动，以及单一数据源如何保持父组件<code>state</code>。诚然，这个示例有点做作，但是应该能用来说明数据和回调是如何在 React 组件之间传递的。
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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: 应该渲染<code>MyApp</code>组件。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyApp)); return mockedComponent.find('MyApp').length === 1; })());
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- text: 应该渲染<code>GetInput</code>组件。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyApp)); return mockedComponent.find('GetInput').length === 1; })());
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- text: 应该渲染<code>RenderInput</code>组件。
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyApp)); return mockedComponent.find('RenderInput').length === 1; })());
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- text: <code>GetInput</code>组件应该接收<code>MyApp</code>的 state 属性<code>inputValue</code>作为 props，并包含一个修改<code>MyApp</code>state 的<code>input</code>元素。
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyApp)); const state_1 = () => { mockedComponent.setState({inputValue: ''''}); return waitForIt(() => mockedComponent.state() )}; const state_2 = () => { mockedComponent.find(''input'').simulate(''change'', {target: {value: ''TestInput''}}); return waitForIt(() => mockedComponent.state() )}; const updated_1 = await state_1(); const updated_2 = await state_2(); assert(updated_1.inputValue === '''' && updated_2.inputValue === ''TestInput''); }; '
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- text: <code>RenderInput</code>组件应该接收<code>MyApp</code>state 属性<code>inputValue</code>作为 props。
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyApp)); const state_1 = () => { mockedComponent.setState({inputValue: ''TestName''}); return waitForIt(() => mockedComponent )}; const updated_1 = await state_1(); assert(updated_1.find(''p'').text().includes(''TestName'')); }; '
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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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class MyApp 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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inputValue: ''
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}
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this.handleChange = this.handleChange.bind(this);
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}
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handleChange(event) {
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this.setState({
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inputValue: event.target.value
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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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{ /* change code below this line */ }
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{ /* change code above this line */ }
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</div>
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);
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}
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};
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class GetInput 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 (
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<div>
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<h3>Get Input:</h3>
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<input
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value={this.props.input}
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onChange={this.props.handleChange}/>
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</div>
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);
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}
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};
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class RenderInput 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 (
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<div>
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<h3>Input Render:</h3>
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<p>{this.props.input}</p>
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</div>
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);
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}
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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(<MyApp />, 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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class MyApp 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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inputValue: ''
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}
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this.handleChange = this.handleChange.bind(this);
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}
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handleChange(event) {
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this.setState({
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inputValue: event.target.value
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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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<GetInput
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input={this.state.inputValue}
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handleChange={this.handleChange}/>
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<RenderInput
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input={this.state.inputValue}/>
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</div>
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);
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}
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};
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class GetInput 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 (
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<div>
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<h3>Get Input:</h3>
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<input
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value={this.props.input}
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onChange={this.props.handleChange}/>
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</div>
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);
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}
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};
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class RenderInput 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 (
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<div>
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<h3>Input Render:</h3>
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<p>{this.props.input}</p>
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</div>
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);
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}
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};
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```
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</section>
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