Can´t access props after using CombineReducer

问题:

My previous React-Redux implementation was working, but after I tried to implement the combineReducer function with seperated files, an error is thrown that I don´t really understand. Hope some of you can help me!

ERROR: Uncaught TypeError: this.props.todos.map is not a function

My Reference for that Code was the Async Example of the Redux-Doc´s. But I stated with another example and the change from each examples are not documented in the doc´s.

The first code I will show, is that I had (working):

MyStore

import { createStore, applyMiddleware } from 'redux'
import thunkMiddleware from 'redux-thunk'
import createLogger from 'redux-logger'
import addItem from '../reducers/addItem'

export default function configureStore(preloadedState) {
   const store = createStore(
    addItem,
    preloadedState,
    applyMiddleware(thunkMiddleware, createLogger())
)

if (module.hot) {
    // Enable Webpack hot module replacement for reducers
    module.hot.accept('../reducers', () => {
        const nextRootReducer = require('../reducers').default
        store.replaceReducer(nextRootReducer)
   })
}

    return store
}

My Reducer

export default (state = ['Test'], action) => {
    switch (action.type){
       case 'ADD_ITEM':
        //return action.item
        return [
            ...state,
            {
                id: action.id,
                text: action.item
            }
        ]
    default:
        return state

    }
 }

Actions

export default function addItem(item){
   console.log("addTOdo")
   return {
    type: 'ADD_ITEM',
    id: nextTodoId++,
    item
   }
 }

And the subComponent where the input is finally rendered

 import React, { Component, PropTypes } from 'react'
 import { connect } from 'react-redux'

 export default class TodoList extends Component {

render() {
    const posts = this.props
    const isEmpty = posts.length === 0
    return (

        <div>
            <h3>Meine Aufgaben</h3>
            <ul>
                {isEmpty
                    ? <h3>Sie haben noch keinen Todo´s angelegt</h3>
                    : <h3>Ihre Ergebnisse</h3>
                }
                {this.props.todos.map((todo, i) => <li key={i}>{todo.text}       </li>)}
            </ul>
        </div>
        )
      }
  }
  const mapStateToProp = state => ({todos: state})

  export default connect (mapStateToProp)(TodoList)

What I have change:

First, I created another Reducers File, called Index where I imported the addItem Reducer and exported the rootReducer:

import {combineReducers} from 'redux'
import addItem from './addItem'
import getItem from './getItem'

const rootReducer = combineReducers({
   addItem,
   getItem
 })

 export default rootReducer

After that, I changed the Store to import the rootReducer and put it´s reference in the Store (just the changes to configureStore):

import rootReducer from '../reducers/index'

 const store = createStore(
    rootReducer,
    preloadedState,
    applyMiddleware(thunkMiddleware, createLogger())
)

I don´t know if that Information is also required, but here is my Container Component:

import React, { Component, PropTypes } from 'react'
import AddTodo from '../components/AddTodo'
import TodoList from '../components/TodoList'
import { connect } from 'react-redux'
import addItem from '../actions/addItem'
import getItems from '../actions/getItems'

class App extends Component {
  constructor(props) {
    super(props)
    this.handleClick = this.handleClick.bind(this)
    this.state = {text: ''}
}

handleClick(e){
    console.log(e);
    const {dispatch} = this.props
    dispatch(addItem(e));
}

componentDidMount(){
    console.log("COMPONENT MOUNT");
    const {dispatch} = this.props
  //  dispatch(getItems())
}

componentWillReceiveProps(nextProps) {
    console.log("GETTT IT");
    console.log(nextProps)
}

render() {

    return (
        <div>
        < h1 > Hallo </h1>
            <AddTodo handleAddItem={this.handleClick}/>
            <TodoList/>
        </div>
    )
  }
}

App.propTypes = {
    dispatch: PropTypes.func.isRequired
}

function mapStateToProps(state){
  return {
    AddTodo
 }
}

export default connect (mapStateToProps)(App)

I hope this issue is not to basic and someone can help me. Thanks in advance!

回答1:

If you inspect your redux state you will see that the following code sets up 2 more keys in the state (addItem and getItem):

const rootReducer = combineReducers({
   addItem,
   getItem
 })

So, now to connect todos you need to one of the 2 new keys. If todos is not defined on those, then you need to add the reducer of todos to the combineReducers call.

So this needs to map to a valid location in state:

const mapStateToProp = state => ({todos: state})