rootReducer

Question

我尝试了简单的react，redux，ajax工作示例并遵循Reddit API tutorial，但我无法创建存储并获得错误：

Uncaught Error: Expected the reducer to be a function.

index.jsx

...

import { createStore, applyMiddleware } from 'redux'
var thunkMiddleware = require('redux-thunk');
var createLogger = require('redux-logger');
var rootReducer = require('./reducers.js');

        const loggerMiddleware = createLogger();

        function configureStore(initialState) {
            return createStore(
                rootReducer,
                initialState,
                applyMiddleware(
                    thunkMiddleware,
                    loggerMiddleware
                )
            )
        }

        const store = configureStore();

...

rootReducer.js

import { combineReducers } from 'redux';

function products(state = {
    isFetching: false,
    didInvalidate: false,
    items: []
}, action) {
    switch (action.type) {
        case 'REQUEST_PRODUCTS':
            return Object.assign({}, state, {
                isFetching: true,
                didInvalidate: false
            })
        case 'RECEIVE_PRODUCTS':
            return Object.assign({}, state, {
                isFetching: false,
                didInvalidate: false,
                items: action.posts,
                lastUpdated: action.receivedAt
            })
        default:
            return state
    }
}

function specialPosts(state = { }, action) {
    switch (action.type) {
        case RECEIVE_SPECPOSTS:
        case REQUEST_SPECPOSTS:
            return Object.assign({}, state, {
                req: true
            })
        default:
            return state
    }
}

const rootReducer = combineReducers({
    products,
    specialPosts
});

export default rootReducer;

rootReducer的类型是对象，但为什么呢？我应该将createStore功能更改为rootReducer.default吗？

return createStore(
    rootReducer.default,
    initialState,
    applyMiddleware(
        thunkMiddleware,
        loggerMiddleware
     )
)

的package.json

"redux-logger": "^2.6.1",
"react-redux": "^4.4.1",
"react-redux-provide": "^5.2.3",
"redux": "^3.3.1",
"redux-thunk": "^2.0.1",

Answer 1

问题是由于rootReducer被＆＃34;要求＆＃34; （ES5）：

var rootReducer = require('./reducers.js');

如果您通过ES6方法导入它，它将正确保存rootReducer.js＆＃39;默认自动进入rootReducer：

import rootReducer from './reducers';

我看到你在那个文件中混合了ES5（require）和ES6（import）......我也在混合我的项目，这就是我遇到这个问题的原因。可以在此处找到更多信息：https://medium.com/@kentcdodds/misunderstanding-es6-modules-upgrading-babel-tears-and-a-solution-ad2d5ab93ce0#.2x2p2dx3m

Answer 2

state.products

然后从各个reducer函数返回的初始状态自动创建初始状态。可以state.specialPosts和jokesApi.js

访问这些单独的州

Answer 3

rootReducer

/* index.js */

import AppReducer from './reducers';
// import {AppReducer} from './reducers';
// bugs : must be a root reducer, can not be use as a module









/* reducers.js */ 

// initial state
const initialState = {
    angular: 0,
    react: 0,
    vuejs: 0
};


// reducers update state 
const AppReducers = (state = initialState, action) => {
    switch (action.type) {
        case 'VOTE_ANGULAR':
            console.log("Vote Angular!");
            return (
                Object.assign(
                    {}, 
                    state, 
                    {
                        angular: state.angular + 1
                    }
                )
            );
        case 'VOTE_REACT':
            console.log("Vote React!");
            return (
                Object.assign(
                    {}, 
                    state, 
                    {
                        react: state.react + 1
                    }
                )
            );
        case 'VOTE_VUEJS':
            console.log("Vote Vue.jsc!");
            return (
                Object.assign(
                    {}, 
                    state, 
                    {
                        vuejs: state.vuejs + 1
                    }
                )
            );
        default:
            return state;
    }
};

export {AppReducers};
export default AppReducers;

Answer 4

我使用VS Code Insiders，有时更改无法正确保存。因此，如果您按照上述所有操作并且错误仍然存在，则转到每个文件并按STRG + S.它为我解决了这个问题。

Answer 5

创建存储区时，第一个参数必须是表示reduce（ ()=>[] ）参数的函数

错误：

import {createStore,applyMiddleware} from 'redux';


export default function configureStore(initialState) {
  return createStore(
    [],
    {},
    applyMiddleware()
  );
}

解决方案：

import {createStore,applyMiddleware} from 'redux';


export default function configureStore(initialState) {
  return createStore(
    ()=>[],
    {},
    applyMiddleware()
  );
}

Answer 6

当您看到错误时：

<块引用>

未捕获的错误：期望 reducer 是一个函数

这并不一定意味着 reducer 不是函数。如果您遇到此错误，您应该尝试使用仅 reducer 创建商店。像这样：

createStore(reducer)

这可能有效。

就我而言，第二个参数是错误的，因为我没有以正确的顺序调用 compose 和 applyMiddleware。所以这是一个正确的设置，似乎在我的情况下有效：


export const createDebugStore = () => {
    const options: EnhancerOptions = {}
    const composeFunc = (typeof window !== 'undefined' && composeWithDevTools(options)) || compose;
    const enhancer = composeFunc(applyMiddleware());

    return createStore((state: any) => state || {}, enhancer);
}

React + Redux - 未捕获错误：期望reducer成为一个函数

6 个答案:

rootReducer