freeCodeCamp/connect-redux-to-the-messages-app.md at d23feadc1f000fdeb8d3ef994157bfeef8d233be

Files

Oliver Eyton-Williams 41b7a33100 fix: replace .chinese.md extension with .md

2020-09-29 22:09:05 +02:00

7.3 KiB

Raw Blame History

id, title, challengeType, forumTopicId, localeTitle

id	title	challengeType	forumTopicId	localeTitle
5a24c314108439a4d4036148	Connect Redux to the Messages App	6	301427	将 Redux 连接到 Messages App

Description

知道connect怎么实现 React 和 Redux 的连接后，我们可以在 React 组件中应用上面学到的内容。在上一课，连接到 Redux 的组件命名为Presentational，这个命名不是任意的，这样的术语通常是指未直接连接到 Redux 的 React 组件，他们只负责执行接收 props 的函数来实现 UI 的呈现。与上一挑战相比，本挑战需要把容器组件连接到 Redux。这些组件通常负责把 actions 分派给 store，且经常给子组件传入 store state 属性。

Instructions

到目前为止，我们的编辑器上已包含了整个章节的代码，唯一不同的是，React 组件被重新命名为Presentational，即展示层组件。创建一个新组件，保存在名为Container的常量中。这个常量用connect把Presentational组件和 Redux 连接起来。然后，在AppWrapper中渲染 React Redux 的Provider组件，给Provider传入 Reduxstore属性并渲染Container为子组件。完成这些，消息 app 应用会再次渲染页面。

Tests

tests:
  - text: <code>AppWrapper</code>应渲染该页面。
    testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('AppWrapper').length === 1; })());
  - text: <code>Presentational</code>组件应渲染<code>h2</code>、<code>input</code>、<code>button</code>、<code>ul</code>四个元素。
    testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); return mockedComponent.find('Presentational').length === 1; })());
  - text: <code>Presentational</code>组件应渲染<code>h2</code>、<code>input</code>、<code>button</code>、<code>ul</code>四个元素。
    testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); const PresentationalComponent = mockedComponent.find('Presentational'); return ( PresentationalComponent.find('div').length === 1 && PresentationalComponent.find('h2').length === 1 && PresentationalComponent.find('button').length === 1 && PresentationalComponent.find('ul').length === 1 ); })());
  - text: <code>Presentational</code>组件应接收 Redux store 的<code>消息</code>属性。
    testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); const PresentationalComponent = mockedComponent.find('Presentational'); const props = PresentationalComponent.props(); return Array.isArray(props.messages); })());
  - text: <code>Presentational</code>组件应接收创建 action 的函数<code>submitMessage</code>属性。
    testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(AppWrapper)); const PresentationalComponent = mockedComponent.find('Presentational'); const props = PresentationalComponent.props(); return typeof props.submitNewMessage === 'function'; })());

Challenge Seed

// Redux:
const ADD = 'ADD';

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

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

const store = Redux.createStore(messageReducer);

// React:
class Presentational 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() {
    const currentMessage = this.state.input;
    this.setState({
      input: '',
      messages: this.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>
    );
  }
};

// React-Redux:
const mapStateToProps = (state) => {
  return { messages: state }
};

const mapDispatchToProps = (dispatch) => {
  return {
    submitNewMessage: (newMessage) => {
       dispatch(addMessage(newMessage))
    }
  }
};

const Provider = ReactRedux.Provider;
const connect = ReactRedux.connect;

// 在此定义 Container 组件：


class AppWrapper extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    // 完成返回声明：
    return (null);
  }
};

After Test

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

Solution

// Redux:
const ADD = 'ADD';

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

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

const store = Redux.createStore(messageReducer);

// React:
class Presentational 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() {
    const currentMessage = this.state.input;
    this.setState({
      input: '',
      messages: this.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>
    );
  }
};

// React-Redux:
const mapStateToProps = (state) => {
  return { messages: state }
};

const mapDispatchToProps = (dispatch) => {
  return {
    submitNewMessage: (newMessage) => {
       dispatch(addMessage(newMessage))
    }
  }
};

const Provider = ReactRedux.Provider;
const connect = ReactRedux.connect;

// define the Container component here:
const Container = connect(mapStateToProps, mapDispatchToProps)(Presentational);

class AppWrapper extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    // complete the return statement:
    return (
      <Provider store={store}>
        <Container/>
      </Provider>
    );
  }
};

7.3 KiB Raw Blame History Unescape Escape