在 Redux 中 Action 不会触发 reducer

Question

我是 redux 的新手，正在尝试使用 Contentful API 获取内容。由于某种原因，我调用的操作没有到达减速器。我附上了我认为相关的代码，任何贡献都将受到高度赞赏。

actions/index.js

import axios from 'axios';

const API_BASE_URL = 'https://cdn.contentful.com';
const API_SPACE_ID = 'xxxxxxxxxxxxx';
const API_KEY ='xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';

const FETCH_CONTENT = 'fetch_content';

export function fetchContent() {
  const request = axios.get(`${API_BASE_URL}/spaces/${API_SPACE_ID}/environments/master/entries?access_token=${API_KEY}`);
  return {
    type: FETCH_CONTENT,
    payload: request
  };
  }

reducers/index.js

import { combineReducers } from 'redux';
import ContentReducer from './reducer-content';

const rootReducer = combineReducers({
  contents: ContentReducer
});

export default rootReducer;

reducer-content.js

import {FETCH_CONTENT} from '../actions';
const INITIAL_STATE = { all: [] };

export default function(state = INITIAL_STATE, action){
  switch(action.type){
    case FETCH_CONTENT:
      return { ...state, all: action.payload.data.items };

  default:
  return state;
  }
}

index.js

import React from 'react';
import ReactDOM from 'react-dom';
import { Provider } from 'react-redux';
import { createStore, applyMiddleware } from 'redux';
import { BrowserRouter, Route, Switch } from "react-router-dom";
import promise from 'redux-promise';
import { logger } from 'redux-logger'


import ContentIndex from './components/content-index';
import reducers from './reducers';

const createStoreWithMiddleware = applyMiddleware(promise, logger)(createStore);

ReactDOM.render(
  <Provider store={createStoreWithMiddleware(reducers)}>
    <BrowserRouter>
      <div>
      <Route  path = "/" component = {ContentIndex}/>
    </div>
    </BrowserRouter>

  </Provider>
  , document.querySelector('.container'));

组件/内容索引.js

import React, {Component} from 'react';
import {fetchContent} from '../actions';
import {connect} from 'react-redux';
import _ from 'lodash';

class ContentIndex extends Component {
  componentDidMount(){
    this.props.fetchContent();
  }

  renderContent(props){
    return this.props.contents.map((content, index) => {
      return (
        <article key={content.sys.id}>
          <h3>{content.fields.name}</h3>
          <p>{content.fields.website}</p>
        </article>
      );
    });
  }

  render(){
    return(
      <div>
      <h3>Content</h3>
      {this.renderContent()}
      </div>
    );
  }
}

const mapStateToProps = (state) => {
  return {contents: state.contents.all};
}
// export default CharacterIndex;
export default connect(mapStateToProps, {fetchContent})(ContentIndex);

Answer 1

更新

看来我在这里错了（感谢@Dave Newton 的 cmets）。 redux-promise 等待一个承诺，如果它收到一个承诺，则解决它并分派该值。所以，在这里使用 async 函数和使用 action creator 是没有用的。

---

您正在使用redux-promise，我不知道它是如何处理这种情况的，但在其 Github 存储库中有一个 redux-actions 的示例，它使用异步函数。我对redux-thunk 更熟悉，但在您的情况下，在这里使用异步操作创建器可能更合适。

试试这个：

export async function fetchContent() {
  const request = await axios.get(`${API_BASE_URL}/spaces/${API_SPACE_ID}/environments/master/entries?access_token=${API_KEY}`);
  return {
    type: FETCH_CONTENT,
    payload: request
  };
}

Answer 2

axios.get() 返回承诺。

所以你需要使用 async / await。

Answer 3

您可以通过执行以下操作来简化代码并避免调度异步操作和需要使用 redux 中间件：

• 将fetchContent() 转换为异步函数，该函数返回带有有效负载中项目的操作
• 创建一个mapDispatchToProps，它创建一个函数来调度fetchContent()返回的操作

fetchContent() 看起来像这样：

export async function fetchContent() {
  const request = await axios.get(`${API_BASE_URL}/spaces/${API_SPACE_ID}/environments/master/entries?access_token=${API_KEY}`);
  return {
    type: FETCH_CONTENT,
    payload: request.data.items
  };
}

connect 看起来像这样：

const mapStateToProps = (state) => {
  return {contents: state.contents.all};
}

const mapDispatchToProps = (dispatch) => {
  return {
    loadItems: () => fetchContent().then(action => dispatch(action))
  }
}

// export default CharacterIndex;
export default connect(mapStateToProps, mapDispatchToProps)(ContentIndex);

你的减速器看起来像这样：

export default function(state = INITIAL_STATE, action){
  switch(action.type){
    case FETCH_CONTENT:
      return { ...state, all: action.payload };

  default:
  return state;
  }
}

componentDidMount() 看起来像这样：

  componentDidMount(){
    this.props.loadItems();
  }