如何在 redux 中发出 AJAX 请求

IT技术 ajax reactjs request redux
2021-04-14 11:30:37

据我所知,我必须在创建中编写请求。如何在行动中使用Promise来提交请求?我正在获取数据。然后在reducer中创建新状态。在连接中绑定动作和减速器。但我不知道如何使用 promise 进行请求。

行动

import $ from 'jquery';
export const GET_BOOK = 'GET_BOOK';

export default function getBook() {
  return {
    type: GET_BOOK,
    data: $.ajax({
      method: "GET",
      url: "/api/data",
      dataType: "json"
    }).success(function(data){
      return data;
    })
  };
}

减速器

import {GET_BOOK} from '../actions/books';

const booksReducer = (state = initialState, action) => {
  switch (action.type) {
    case GET_BOOK:
      return state;
    default:
      return state;
  }
};

export default booksReducer;

Container 如何在容器中显示数据?

import React, { Component, PropTypes } from 'react';
import { connect } from 'react-redux';
import getBook  from '../actions/books';
import Radium from 'radium';
import {Link} from 'react-router';

function mapStateToProps(state) {
  return {
    books: state.data.books,
  };
}

function mapDispatchToProps(dispatch) {
  return {
    getBooks: () => dispatch(getBook()),
  };
}

@Radium
@connect(mapStateToProps, mapDispatchToProps)
class booksPage extends Component {
  static propTypes = {
    getBooks: PropTypes.func.isRequired,
    books: PropTypes.array.isRequired,
  };

  render() {
    const {books} = this.props;
    return (
      <div>
        <Link to={`/authors`}><MUIButton style="flat">All Authors</MUIButton></Link>
        <ul>
          {books.map((book, index) =>
            <li key={index}>
              <Link to={`/book/${book.name}`}><MUIButton style="flat"><div class="mui--text-black mui--text-display4">
                "{book.name}"</div></MUIButton></Link>
              <Link to={`/author/${book.author}`}><MUIButton style="flat"><div class="mui--text-black mui--text-display4">
                {book.author}</div></MUIButton></Link>
            </li>
          )}
        </ul>
      </div>
    );
  }
}

export default booksPage;
5个回答

由于您已经在使用 redux,您可以应用redux-thunk允许您定义异步操作的中间件。

安装与使用:Redux-thunk

export function fetchBook(id) {
 return dispatch => {
   dispatch(setLoadingBookState()); // Show a loading spinner
   fetch(`/book/${id}`, (response) => {
     dispatch(doneFetchingBook()); // Hide loading spinner
     if(response.status == 200){
       dispatch(setBook(response.json)); // Use a normal function to set the received state
     }else { 
       dispatch(someError)
     }
   })
 }
}

function setBook(data) {
 return { type: 'SET_BOOK', data: data };
}

您应该使用Redux 文档中描述的异步操作

这是异步操作的减速器示例。

const booksReducer = (state = {}, action) => {
  switch (action.type) {
    case 'RESOLVED_GET_BOOK':
      return action.data;
    default:
      return state;
  }
};

export default booksReducer;

然后创建异步操作。

export const getBook() {
  return fetch('/api/data')
    .then(response => response.json())
    .then(json => dispatch(resolvedGetBook(json)))
}

export const resolvedGetBook(data) {
  return {
    type: 'RESOLVED_GET_BOOK',
    data: data
  }
}

几个注意事项:

  • 我们可以使用 redux-thunk 中间件返回 Promise(而不是 Object)。
  • 不要使用 jQuery ajax 库。使用其他专门用于执行此操作的库(例如 fetch())。我使用axios http 客户端
  • 请记住,在 redux 中,您只能在 reducer 中使用纯函数。不要在减速器内进行 ajax 调用。
  • 阅读 redux 文档中的完整指南。

您应该能够dispatch在回调中使用(如果您将其作为参数传递):

export default function getBook(dispatch) {
  $.ajax({
      method: "GET",
      url: "/api/data",
      dataType: "json"
    }).success(function(data){
      return dispatch({type:'GET_BOOK', data: data});
    });
}

然后,传递dispatch给动作:

function mapDispatchToProps(dispatch) {
  return {
    getBooks: () => getBook(dispatch),
  };
}

现在,您应该可以访问action.data减速器中属性:

const booksReducer = (state = initialState, action) => {
  switch (action.type) {
    case GET_BOOK:
      //action.data  <--- here
      return state;
    default:
      return state;
  }
};
如果你这样减少,那么state.data.books在你的mapStateToProps. console.log那里做一个,看看是什么state
2021-05-22 11:30:37
谢谢,但现在我收到警告:失败的 propType:booksbooksPage. 检查Connect(booksPage).warning @ (program):45 (program):45的渲染方法警告:getDefaultProps 仅用于经典的 React.createClass 定义。改用名为的静态属性defaultProps
2021-05-29 11:30:37
你有没有减少action.data进入状态?
2021-05-30 11:30:37
Object.assign({}, state, { books: action.data.books, author: action.data.authors });
2021-06-11 11:30:37
我使用了 console.log,而 state.data 等于 0。这意味着 GET_BOOK 不起作用。但为什么?
2021-06-19 11:30:37

您可能想要分离关注点,以保持动作创建者“纯”。

解决方案; 写一些中间件。以此为例(使用超级代理)。

import Request from 'superagent';

const successHandler = (store,action,data) => {

    const options = action.agent;
    const dispatchObject = {};
    dispatchObject.type = action.type + '_SUCCESS';
    dispatchObject[options.resourceName || 'data'] = data;
    store.dispatch(dispatchObject);
};

const errorHandler = (store,action,err) => {

    store.dispatch({
        type: action.type + '_ERROR',
        error: err
    });
};

const request = (store,action) => {

    const options = action.agent;
    const { user } = store.getState().auth;
    let method = Request[options.method];

    method = method.call(undefined, options.url)

    if (user && user.get('token')) {
        // This example uses jwt token
        method = method.set('Authorization', 'Bearer ' + user.get('token'));
    }

    method.send(options.params)
    .end( (err,response) => {
        if (err) {
            return errorHandler(store,action,err);
        }
        successHandler(store,action,response.body);
    });
};

export const reduxAgentMiddleware = store => next => action => {

    const { agent } = action;

    if (agent) {
        request(store, action);
    }
    return next(action);
};

将所有这些放在一个module中。

现在,您可能有一个名为“auth”的动作创建者:

export const auth = (username,password) => {

    return {
        type: 'AUTHENTICATE',
        agent: {
            url: '/auth',
            method: 'post',
            resourceName: 'user',
            params: {
                username,
                password
            }
        }
    };
};

属性“代理”将由中间件获取,中间件通过网络发送构造的请求,然后将传入的结果分派到您的商店。

在定义钩子之后,您的减速器会处理所有这些:

import { Record } from 'immutable';

const initialState = Record({
    user: null,
    error: null
})();

export default function auth(state = initialState, action) {

    switch (action.type) {

        case 'AUTHENTICATE':

            return state;

        case 'AUTHENTICATE_SUCCESS':

            return state.merge({ user: action.user, error: null });

        case 'AUTHENTICATE_ERROR':

            return state.merge({ user: null, error: action.error });

        default:

            return state;
    }
};

现在将所有这些注入到您的视图逻辑中。我以react为例。

import React from 'react';
import ReactDOM from 'react-dom';

/* Redux + React utils */
import { createStore, applyMiddleware, bindActionCreators } from 'redux';
import { Provider, connect } from 'react-redux';

// thunk is needed for returning functions instead 
// of plain objects in your actions.
import thunkMiddleware from 'redux-thunk';

// the logger middleware is useful for inspecting data flow
import createLogger from 'redux-logger';

// Here, your new vital middleware is imported
import { myNetMiddleware } from '<your written middleware>';

/* vanilla index component */
import _Index from './components';

/* Redux reducers */
import reducers from './reducers';

/* Redux actions*/
import actionCreators from './actions/auth';


/* create store */
const store = createStore(
    reducers,
    applyMiddleware(
        thunkMiddleware,
        myNetMiddleware
    )
);

/* Taint that component with store and actions */
/* If all goes well props should have 'auth', after we are done */
const Index = connect( (state) => {

    const { auth } = state;

    return {
        auth
    };
}, (dispatch) => {

    return bindActionCreators(actionCreators, dispatch);
})(_Index);

const provider = (
    <Provider store={store}>
        <Index />
    </Provider>
);

const entryElement = document.getElementById('app');
ReactDOM.render(provider, entryElement);

所有这些都意味着你已经使用 webpack、rollup 或其他东西建立了一个管道,从 es2015 转译和react,到 vanilla js。

考虑使用新的 thunk API

export const load = createAsyncThunk(
  'example/api',
  async (arg, thunkApi) => {
    const response = await fetch('http://example.api.com/api')

    if (response.status === 200) {
      const json = await response.json()
      return json
  },
)

此外,在新的 redux 模板应用程序中,动作是 reducer/slice 的一部分,您可以使用 extraReducers 来响应与异步动作状态相关的事件。以这种方式使用 redux 要简单得多。

在此处查看异步 thunk 的文档:https : //redux.js.org/usage/writing-logic-thunks

您可以在https://runkiss.blogspot.com/2021/11/create-redux-app-with-async-ajax-calls.html帖子中看到完整的示例