React / Redux:为什么mapStateToProps()使我的数组存储状态消失?

时间:2017-11-05 19:58:48

标签: redux react-redux redux-thunk

在我的商店中,我有一个具有此形状的状态:{posts: [{...},{...}]},但是当我在Home.js中使用mapStateToProps()时,状态返回{posts: []},其中包含一个空数组(其中有曾经是商店州的一个数组)。

我是否错误地使用mapStateToProps()或问题是否源于Redux循环的其他部分?

API提取我暂时使用,位于actions.js

// api

const API = "http://localhost:3001"

let token = localStorage.token
if (!token) {
    token = localStorage.token = Math.random().toString(36).substr(-8)
}

const headers = {
    'Accept': 'application/json',
    'Authorization': token
}

// gets all posts
const getAllPosts = token => (
    fetch(`${API}/posts`, { method: 'GET', headers })
);

动作和动作创建者,使用thunk中间件:

// actions.js

export const REQUEST_POSTS = 'REQUEST_POSTS';
function requestPosts (posts) {
    return {
        type: REQUEST_POSTS,
        posts
    }
}

export const RECEIVE_POSTS = 'RECEIVE_POSTS';
function receivePosts (posts) {
    return {
        type: RECEIVE_POSTS,
        posts,
        receivedAt: Date.now()
    }
}

// thunk middleware action creator, intervenes in the above function
export function fetchPosts (posts) {
    return function (dispatch) {
        dispatch(requestPosts(posts))
        return getAllPosts()
               .then(
                    res => res.json(),
                    error => console.log('An error occured.', error)
                )
               .then(posts => 
                    dispatch(receivePosts(posts))
                )
    }
}

减速机:

// rootReducer.js

function posts (state = [], action) {
    const { posts } = action

    switch(action.type) {
        case RECEIVE_POSTS :
            return posts;
        default : 
            return state;
    }
}

临时包含Redux存储的根组件:

// index.js (contains store)

const store = createStore(
  rootReducer,
  composeEnhancers(
    applyMiddleware(
        logger, // logs actions
        thunk // lets us dispatch() functions
    )
  )
)

store
  .dispatch(fetchPosts())
  .then(() => console.log('On store dispatch: ', store.getState())) // returns expected

ReactDOM.render(
    <BrowserRouter>
        <Provider store={store}>
            <Quoted />
        </Provider>
    </BrowserRouter>, document.getElementById('root'));
registerServiceWorker();

主要组成部分:

// Home.js
function mapStateToProps(state) {
    return {
        posts: state
    }
}


export default connect(mapStateToProps)(Home)

在Home.js组件中,console.log('Props', this.props)返回{posts:[]},我希望{posts:[{...},{...}}}。

***编辑: 在发送之前和reducer中的操作中添加console.log()之后,这是控制台输出: Console output link (not high enough rep to embed yet)

1 个答案:

答案 0 :(得分:2)

redux存储应该是一个对象,但似乎它在根reducer中被初始化为一个数组。您可以尝试以下方法:

const initialState = {
    posts: []
}

function posts (state = initialState, action) {

    switch(action.type) {
        case RECEIVE_POSTS :
            return Object.assign({}, state, {posts: action.posts})
        default : 
            return state;
    }
}

然后在mapStateToProps函数中:

function mapStateToProps(state) {
    return {
        posts: state.posts
    }
}