1
我正在使用react和redux的项目，我已经足够新，所以我想更好地了解如何使用redux-thunk和redux一起赞成。 下面你可以看到我的文件，在我的动作中，我创建了一个获取通用函数apiFetch（），以便每次需要获取时使用。这个函数返回一个承诺，我要在loadBooks（）中解析，代码正在工作，记录被上传，但是当我检查行为日志时，我发现第一个行为是未定义的，在有BOOKS_LOADING之后， LOAD_BOOKS，BOOKS_LOADING和LOAD_BOOKS_SUCCESS。以正确的方式使用redux-promise-middleware的redux-thunk
我有关于2个问题：
1）为什么是第一个未定义的动作，我已经LOAD_BOOKS而不是比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）举例来说，如果为获取网址是错误的，我期望看到的动作LOAD_BOOKS_ERROR，这实际上是对数的结果是：
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（），但是正常的读取函数，所有工作都正常，也是错误的一部分，除了LOAD_BOOKS不是LOAD_BOOKS_START。
非常感谢您的帮助！
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;
动作/ 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);
});
});
}),
});
};
常数/的application.js
export const LOAD_BOOKS = 'LOAD_BOOKS';
减速器/ 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;
}
}