freeCodeCamp/curriculum/challenges/chinese/03-front-end-libraries/react-and-redux/use-provider-to-connect-redux-to-react.md

---
id: 5a24c314108439a4d4036144
title: 使用 Provider 连接 Redux 和 React
challengeType: 6
forumTopicId: 301435
dashedName: use-provider-to-connect-redux-to-react
---

# --description--

在上一挑战中，你创建了 Redux store 和 action，分别用于处理消息数组和添加新消息。下一步要为 React 提供访问 Redux store 及发起更新所需的 actions。`react-redux`包可帮助我们完成这些任务。

React Redux 提供的 API 有两个关键的功能：`Provider`和`connect`。你会在另一个挑战中学`connect`。`Provider`是 React Redux 包装 React 应用的 wrapper 组件，它允许你访问整个组件树中的 Redux`store`及`dispatch（分发）`方法。`Provider`需要两个 props：Redux store 和 APP 应用的子组件。用于 APP 组件的`Provider`可这样定义：

```jsx
<Provider store={store}>
  <App/>
</Provider>
```

# --instructions--

此时，编辑器上显示的是过去几个挑战中所有代码，包括 Redux store、actions、`DisplayMessages`组件。新出现的代码是底部的`AppWrapper`组件，这个顶级组件可用于渲染`ReactRedux`的`Provider`，并把 Redux 的 store 作为 props 传入。接着，渲染`DisplayMessages`为子组件。完成这些任务后，你会看到 React 组件渲染到页面上。

**注意：** React Redux 在此可作全局变量，因此你可通过点号表示法访问 Provider。利用这一点，编辑器上的代码把`Provider`设置为常量，便于你在`AppWrapper`渲染方法中使用。

# --hints--

`AppWrapper`应渲染。

```js
assert(
  (function () {
    const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
    return mockedComponent.find('AppWrapper').length === 1;
  })()
);
```

`Provider`组件应传入相当于 Redux store 的`store`参数。

```js
(getUserInput) =>
  assert(
    (function () {
      const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
      return getUserInput('index')
        .replace(/\s/g, '')
        .includes('<Providerstore={store}>');
    })()
  );
```

`DisplayMessages`应渲染为`AppWrapper`的子组件。

```js
assert(
  (function () {
    const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
    return (
      mockedComponent.find('AppWrapper').find('DisplayMessages').length === 1
    );
  })()
);
```

`DisplayMessages`组件应渲染 h2、input、button、`ul`四个元素。

```js
assert(
  (function () {
    const mockedComponent = Enzyme.mount(React.createElement(AppWrapper));
    return (
      mockedComponent.find('div').length === 1 &&
      mockedComponent.find('h2').length === 1 &&
      mockedComponent.find('button').length === 1 &&
      mockedComponent.find('ul').length === 1
    );
  })()
);
```

# --seed--

## --after-user-code--

```jsx
ReactDOM.render(<AppWrapper />, document.getElementById('root'))
```

## --seed-contents--

```jsx
// Redux:
const ADD = 'ADD';

const addMessage = (message) => {
  return {
    type: ADD,
    message
  }
};

const messageReducer = (state = [], action) => {
  switch (action.type) {
    case ADD:
      return [
        ...state,
        action.message
      ];
    default:
      return state;
  }
};



const store = Redux.createStore(messageReducer);

// React:

class DisplayMessages extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      input: '',
      messages: []
    }
    this.handleChange = this.handleChange.bind(this);
    this.submitMessage = this.submitMessage.bind(this);
  }
  handleChange(event) {
    this.setState({
      input: event.target.value
    });
  }
  submitMessage() {  
    this.setState((state) => {
      const currentMessage = state.input;
      return {
        input: '',
        messages: state.messages.concat(currentMessage)
      };
    });
  }
  render() {
    return (
      <div>
        <h2>Type in a new Message:</h2>
        <input
          value={this.state.input}
          onChange={this.handleChange}/><br/>
        <button onClick={this.submitMessage}>Submit</button>
        <ul>
          {this.state.messages.map( (message, idx) => {
              return (
                 <li key={idx}>{message}</li>
              )
            })
          }
        </ul>
      </div>
    );
  }
};

const Provider = ReactRedux.Provider;

class AppWrapper extends React.Component {
  // Render the Provider below this line

  // Change code above this line
};
```

# --solutions--

```jsx
// Redux:
const ADD = 'ADD';

const addMessage = (message) => {
  return {
    type: ADD,
    message
  }
};

const messageReducer = (state = [], action) => {
  switch (action.type) {
    case ADD:
      return [
        ...state,
        action.message
      ];
    default:
      return state;
  }
};

const store = Redux.createStore(messageReducer);

// React:

class DisplayMessages extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      input: '',
      messages: []
    }
 this.handleChange = this.handleChange.bind(this);
 this.submitMessage = this.submitMessage.bind(this);
 }
  handleChange(event) {
    this.setState({
      input: event.target.value
    });
  }
  submitMessage() {
    this.setState((state) => {
      const currentMessage = state.input;
      return {
        input: '',
        messages: state.messages.concat(currentMessage)
      };  
    });
  }
  render() {
    return (
      <div>
        <h2>Type in a new Message:</h2>
        <input
          value={this.state.input}
          onChange={this.handleChange}/><br/>
        <button onClick={this.submitMessage}>Submit</button>
        <ul>
          {this.state.messages.map( (message, idx) => {
              return (
                 <li key={idx}>{message}</li>
              )
            })
          }
        </ul>
      </div>
    );
  }
};

const Provider = ReactRedux.Provider;

class AppWrapper extends React.Component {
  // Change code below this line
  render() {
    return (
      <Provider store = {store}>
        <DisplayMessages/>
      </Provider>
    );
  }
  // Change code above this line
};
```