119 lines
5.5 KiB
Markdown
119 lines
5.5 KiB
Markdown
---
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id: 5a24c314108439a4d403617b
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title: Pass a Callback as Props
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challengeType: 6
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isRequired: false
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videoUrl: ''
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localeTitle: 将回调作为道具传递
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---
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## Description
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<section id="description">您可以将<code>state</code>作为道具传递给子组件，但您不仅限于传递数据。您还可以将处理函数或在React组件上定义的任何方法传递给子组件。这是允许子组件与其父组件交互的方式。您可以将方法传递给孩子，就像常规道具一样。它被分配了一个名称，您可以在子组件中的<code>this.props</code>下访问该方法名称。 </section>
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## Instructions
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<section id="instructions">代码编辑器中列出了三个组件。 <code>MyApp</code>组件是将呈现<code>GetInput</code>和<code>RenderInput</code>子组件的父组件。将<code>GetInput</code>组件添加到<code>MyApp</code>的render方法，然后从<code>MyApp</code>的<code>state</code>向它传递一个名为<code>input</code>的prop，该<code>input</code>分配给<code>inputValue</code> 。还要创建一个名为<code>handleChange</code>的prop，并将输入处理程序<code>handleChange</code>给它。接下来，将<code>RenderInput</code>添加到<code>MyApp</code>的render方法，然后创建一个名为<code>input</code>的prop，并将<code>inputValue</code>从<code>state</code>传递给它。完成后，您将能够在<code>GetInput</code>组件中<code>input</code>字段，然后通过props调用其父级中的处理程序方法。这将更新父级<code>state</code>的输入，该输入作为props传递给两个子级。观察数据如何在组件之间流动以及单个事实源如何保持父组件的<code>state</code> 。不可否认，这个例子有点人为，但应该用来说明如何在React组件之间传递数据和回调。 </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: <code>MyApp</code>组件应该呈现。
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyApp)); return mockedComponent.find("MyApp").length === 1; })(), "The <code>MyApp</code> component should render.");'
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- text: <code>GetInput</code>组件应该呈现。
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyApp)); return mockedComponent.find("GetInput").length === 1; })(), "The <code>GetInput</code> component should render.");'
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- text: <code>RenderInput</code>组件应该呈现。
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testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyApp)); return mockedComponent.find("RenderInput").length === 1; })(), "The <code>RenderInput</code> component should render.");'
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- text: <code>GetInput</code>组件应该将<code>MyApp</code>状态属性<code>inputValue</code>作为props接收，并包含一个修改<code>MyApp</code>状态的<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", "The <code>GetInput</code> component should receive the <code>MyApp</code> state property <code>inputValue</code> as props and contain an <code>input</code> element which modifies <code>MyApp</code> state."); }; '
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- text: <code>RenderInput</code>组件应该将<code>MyApp</code>状态属性<code>inputValue</code>作为props接收。
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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"), "The <code>RenderInput</code> component should receive the <code>MyApp</code> state property <code>inputValue</code> as props."); }; '
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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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console.info('after the test');
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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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// solution required
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```
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</section>
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