javascript - 以正确的方式将 redux-thunk 与 redux-promise-middleware 一起使用

Question

我在一个使用 react 和 redux 的项目中工作，我是新手所以我想更好地理解如何一起使用 redux-thunk 和 redux-promise。下面您可以看到我的文件，在我的操作中，我创建了一个获取通用函数 apiFetch() 以便在每次需要获取时使用。这个函数返回一个 promise ，我将在 loadBooks() 中解析，代码正在运行并且记录已上传但是当我检查操作日志时我看到第一个操作是未定义的，在 BOOKS_LOADING 之后， LOAD_BOOKS、BOOKS_LOADING 和 LOAD_BOOKS_SUCCESS。

我有两个问题:

1) 为什么第一个操作未定义并且我有 LOAD_BOOKS 而不是 LOAD_BOOKS_START？

action @ 22:54:37.403 undefined
core.js:112  prev state Object {activeBook: null, booksListing: Object}
core.js:116  action function (dispatch) {
        var url = './src/data/payload.json';
        dispatch(booksIsLoading(true));
        return dispatch({
          type: 'LOAD_BOOKS',
          payload: new Promise(function (resolve) {
…
core.js:124  next state Object {activeBook: null, booksListing: Object}
action @ 22:54:37.404 BOOKS_LOADING
action @ 22:54:37.413 LOAD_BOOKS
action @ 22:54:39.420 BOOKS_LOADING
action @ 22:54:39.425 LOAD_BOOKS_SUCCESS

2) 例如，如果获取的 url 错误，我希望看到操作 LOAD_BOOKS_ERROR，而这是日志的结果:

action @ 23:06:06.837 undefined action @ 23:06:06.837 BOOKS_LOADING
action @ 23:06:06.846 LOAD_BOOKS GET
http://localhost:8000/src/data/payldoad.json 404 (Not Found) error
apiFetch Error: request failed at index.js:66 error 
TypeError: Cannot read property 'json' of undefined at index.js:90

如果我不使用 apiFetch()，而是使用正常的获取函数，则一切正常，也是错误的一部分，除了 LOAD_BOOKS 不是 LOAD_BOOKS_START。

提前感谢您的帮助!

configureStore.js

import { createStore, applyMiddleware, compose, preloadedState } from 'redux';
import reducers from './configureReducer';
import configureMiddleware from './configureMiddleware';

const middleware = configureMiddleware();
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ ||   compose;
const store = createStore(reducers, preloadedState, composeEnhancers(applyMiddleware(...middleware)));
export default store;

actions/index.js

import fetch from 'isomorphic-fetch';

export const booksIsLoading = (bool) => {
  return {
    type: 'BOOKS_LOADING',
    booksLoading: bool,
  };
};

const delay = ms => new Promise(resolve => setTimeout(resolve, ms));

export const apiFetch = (url) => {
  const getPromise = () => (
    fetch(url, {
      method: 'GET',
    })
      .then((response) => {
        if (response.status !== 200) {
          throw Error('request failed');
        }
        return response;
      })
      .catch((err) => {
        console.log('error apiFetch', err);
        // dispatch(fetchBooksError(true));
      })
  );
  return getPromise();
};

export const loadBooks = () => (dispatch) => {
  const url = './src/data/payload.json';
  dispatch(booksIsLoading(true));
  return dispatch({
    type: 'LOAD_BOOKS',
    payload: new Promise((resolve) => {
      delay(2000).then(() => {
        apiFetch(`${url}`)
          // fetch(`${url}`, {
          //   method: 'GET',
          // })
          .then((response) => {
            resolve(response.json());
            dispatch(booksIsLoading(false));
          }).catch((err) => {
            console.log('error', err);
          });
      });
    }),
  });
};

constants/application.js

export const LOAD_BOOKS = 'LOAD_BOOKS';

reducers/reducer_book.js

import initialState from '../model.js';
import * as types from '../constants/application';

export default function (state = initialState, action) {
  switch (action.type) {
    case `${types.LOAD_BOOKS}_SUCCESS`: {
      console.log('reducer', action.payload);
      const data = action.payload.data.items;
      const items = Object.values(data);

      if (items.length > 0) {
        return {
          ...state,
          books: Object.values(data),
          booksFetched: true,
          booksError: false,
        };
      }

      return state;
    }

    case `${types.LOAD_BOOKS}_ERROR`: {
      return {
        ...state,
        booksError: true,
      };
    }

    case 'BOOKS_LOADING':
      return {
        ...state,
        booksLoading: action.booksLoading,
      };

    default:
      return state;
  }
}

Answer 1

您指定中间件的顺序是什么？

以下用法使操作变得不确定:

'applyMiddleware(reduxPromiseMiddleware(), reduxThunk)'

请将顺序更改为:(先敲击!)

'applyMiddleware(reduxThunk, reduxPromiseMiddleware())'