react redux：当使用Connect for mapStateToProps和mapDispatchToProps时仍然为this.props获取空对象

Question

I'm trying to follow this tutorial ( https://medium.com/@stowball/a-dummys-guide-to-redux-and-thunk-in-react-d8904a7005d3 ) on React Redux but am getting an empty object when I print out this.props. It seems like mapStateToProps isn't actually setting this.props since react redux's connect isn't being called, but I'm not sure why

This is what the state should be (like in the tutorial), all I did was change the component's name ItemList to Home

Here's what I'm getting (nothing was mapped to the state):

actions/items.js

export function itemsHasErrored(bool) {
    return {
        type: 'ITEMS_HAS_ERRORED',
        hasErrored: bool
    };
}

export function itemsIsLoading(bool) {
    return {
        type: 'ITEMS_IS_LOADING',
        isLoading: bool
    };
}

export function itemsFetchDataSuccess(items) {
    return {
        type: 'ITEMS_FETCH_DATA_SUCCESS',
        items
    };
}

export function itemsFetchData(url) {
    return (dispatch) => {
        dispatch(itemsIsLoading(true));

        fetch(url)
            .then((response) => {
                if (!response.ok) {
                    throw Error(response.statusText);
                }

                dispatch(itemsIsLoading(false));

                return response;
            })
            .then((response) => response.json())
            .then((items) => dispatch(itemsFetchDataSuccess(items)))
            .catch(() => dispatch(itemsHasErrored(true)));
    };
}

components/Home.js

export class Home extends Component {
  componentDidMount() {
    console.log(this.props)
  }

 render() {

    if (this.props.hasErrored) {
      return <p>Sorry! There was an error loading the items</p>;
    }

    if (this.props.isLoading) {
        return <p>Loading…</p>;
    }

  return (
      <ul>
          {this.props.items.map((item) => (
              <li key={item.id}>
                  {item.label}
              </li>
          ))}
      </ul>
  );    

  }
}


 const mapStateToProps = (state) => {
  return {
      items: state.items,
      hasErrored: state.itemsHasErrored,
      isLoading: state.itemsIsLoading
  };
};

const mapDispatchToProps = (dispatch) => {
  return {
      fetchData: (url) => dispatch(itemsFetchData(url))
  };
};

export default connect(mapStateToProps, mapDispatchToProps)(Home);

reducers/index.js

export function itemsHasErrored(state = false, action) {
    switch (action.type) {
        case 'ITEMS_HAS_ERRORED':
            return action.hasErrored;

        default:
            return state;
    }
}

export function itemsIsLoading(state = false, action) {
    switch (action.type) {
        case 'ITEMS_IS_LOADING':
            return action.isLoading;

        default:
            return state;
    }
}

export function items(state = [], action) {
    switch (action.type) {
        case 'ITEMS_FETCH_DATA_SUCCESS':
            return action.items;

        default:
            return state;
    }
}

store/configureStore.js

import { applyMiddleware, createStore } from 'redux'
import thunk from 'redux-thunk'
import rootReducer from '../reducers'

export default function configureStore(initialState) {
    return createStore(
        rootReducer,
        initialState,
        applyMiddleware(thunk)
    )
} 

App.js

import React, { Component } from 'react'
import { Provider } from 'react-redux'
import configureStore from './store/configureStore'

import { Home }                     from './components/Home'
const store = configureStore()

export default class App extends Component {

    render () {
      return (
        <Provider store={store}>
          <Home />
        </Provider>
      )
    }

  }

index.js (I am using create-react-app boilerplate)

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import registerServiceWorker from './registerServiceWorker';

ReactDOM.render(<App />, document.getElementById('root'));
registerServiceWorker();

Answer 1

The issue is that you're exporting two components... the non-connected (via the named export Home with export class Home... ) and connected (via export default ). Then, you're importing and rendering the non-connected component:

import { Home } from './components/Home'

Since you want to use the connected component, you should be importing the default export like this:

import Home from './components/Home'

You may want to just export the connected component, unless you have some reason to use the unconnected one.