218 lines
5.5 KiB
Markdown
218 lines
5.5 KiB
Markdown
---
|
||
id: 5a24c314108439a4d403617b
|
||
title: 传递回调作为 Props
|
||
challengeType: 6
|
||
forumTopicId: 301400
|
||
dashedName: pass-a-callback-as-props
|
||
---
|
||
|
||
# --description--
|
||
|
||
你可以将`state`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`this.props`下访问该方法的名字。
|
||
|
||
# --instructions--
|
||
|
||
代码编辑器中列出了三个组件。`MyApp`是父组件,`GetInput`和`RenderInput`是它的子组件。将`GetInput`组件添加到`MyApp`的 render 方法,然后将`MyApp`的`state`中的`inputValue`传入名为`input`的 prop。还要创建一个名为`handleChange`的 prop,并将输入处理程序`handleChange`传递给它。
|
||
|
||
接下来,将`RenderInput`添加到`MyApp`中的 render 方法中,然后创建一个名为`input`的 prop,并将`state`中的`inputValue`传递给它。完成后,你将能够在`GetInput`组件中的`input`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`state`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`state`。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。
|
||
|
||
# --hints--
|
||
|
||
应该渲染`MyApp`组件。
|
||
|
||
```js
|
||
assert(
|
||
(function () {
|
||
const mockedComponent = Enzyme.mount(React.createElement(MyApp));
|
||
return mockedComponent.find('MyApp').length === 1;
|
||
})()
|
||
);
|
||
```
|
||
|
||
应该渲染`GetInput`组件。
|
||
|
||
```js
|
||
assert(
|
||
(function () {
|
||
const mockedComponent = Enzyme.mount(React.createElement(MyApp));
|
||
return mockedComponent.find('GetInput').length === 1;
|
||
})()
|
||
);
|
||
```
|
||
|
||
应该渲染`RenderInput`组件。
|
||
|
||
```js
|
||
assert(
|
||
(function () {
|
||
const mockedComponent = Enzyme.mount(React.createElement(MyApp));
|
||
return mockedComponent.find('RenderInput').length === 1;
|
||
})()
|
||
);
|
||
```
|
||
|
||
`GetInput`组件应该接收`MyApp`的 state 属性`inputValue`作为 props,并包含一个修改`MyApp`state 的`input`元素。
|
||
|
||
```js
|
||
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');
|
||
};
|
||
```
|
||
|
||
`RenderInput`组件应该接收`MyApp`state 属性`inputValue`作为 props。
|
||
|
||
```js
|
||
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'));
|
||
};
|
||
```
|
||
|
||
# --seed--
|
||
|
||
## --after-user-code--
|
||
|
||
```jsx
|
||
ReactDOM.render(<MyApp />, document.getElementById('root'))
|
||
```
|
||
|
||
## --seed-contents--
|
||
|
||
```jsx
|
||
class MyApp extends React.Component {
|
||
constructor(props) {
|
||
super(props);
|
||
this.state = {
|
||
inputValue: ''
|
||
}
|
||
this.handleChange = this.handleChange.bind(this);
|
||
}
|
||
handleChange(event) {
|
||
this.setState({
|
||
inputValue: event.target.value
|
||
});
|
||
}
|
||
render() {
|
||
return (
|
||
<div>
|
||
{ /* Change code below this line */ }
|
||
|
||
{ /* Change code above this line */ }
|
||
</div>
|
||
);
|
||
}
|
||
};
|
||
|
||
class GetInput extends React.Component {
|
||
constructor(props) {
|
||
super(props);
|
||
}
|
||
render() {
|
||
return (
|
||
<div>
|
||
<h3>Get Input:</h3>
|
||
<input
|
||
value={this.props.input}
|
||
onChange={this.props.handleChange}/>
|
||
</div>
|
||
);
|
||
}
|
||
};
|
||
|
||
class RenderInput extends React.Component {
|
||
constructor(props) {
|
||
super(props);
|
||
}
|
||
render() {
|
||
return (
|
||
<div>
|
||
<h3>Input Render:</h3>
|
||
<p>{this.props.input}</p>
|
||
</div>
|
||
);
|
||
}
|
||
};
|
||
```
|
||
|
||
# --solutions--
|
||
|
||
```jsx
|
||
class MyApp extends React.Component {
|
||
constructor(props) {
|
||
super(props);
|
||
this.state = {
|
||
inputValue: ''
|
||
}
|
||
this.handleChange = this.handleChange.bind(this);
|
||
}
|
||
handleChange(event) {
|
||
this.setState({
|
||
inputValue: event.target.value
|
||
});
|
||
}
|
||
render() {
|
||
return (
|
||
<div>
|
||
<GetInput
|
||
input={this.state.inputValue}
|
||
handleChange={this.handleChange}/>
|
||
<RenderInput
|
||
input={this.state.inputValue}/>
|
||
</div>
|
||
);
|
||
}
|
||
};
|
||
|
||
class GetInput extends React.Component {
|
||
constructor(props) {
|
||
super(props);
|
||
}
|
||
render() {
|
||
return (
|
||
<div>
|
||
<h3>Get Input:</h3>
|
||
<input
|
||
value={this.props.input}
|
||
onChange={this.props.handleChange}/>
|
||
</div>
|
||
);
|
||
}
|
||
};
|
||
|
||
class RenderInput extends React.Component {
|
||
constructor(props) {
|
||
super(props);
|
||
}
|
||
render() {
|
||
return (
|
||
<div>
|
||
<h3>Input Render:</h3>
|
||
<p>{this.props.input}</p>
|
||
</div>
|
||
);
|
||
}
|
||
};
|
||
```
|