Question

我有一些react-redux项目。我有一些组件，我不想列出api的一些数据。只需在 componentDidMount 方法中从我的组件中调度操作即可获取数据。

刷新页面时，将console.log设置为redux状态。

组件渲染良好，但是当我查看控制台时，有console.log显示我的状态为空，然后正常显示我的状态。.在此过程中，我的组件给我一个错误，我的数据无法显示页面未定义。

所以这是因为我所理解的是fetch方法异步工作，但是当我的redux状态将从api获取数据然后呈现组件时，该怎么办？

这是我的操作：

export const FETCH_DATA_START = 'FETCH_DATA_START'
export const FETCH_DATA_SUCCESS = 'FETCH_DATA_SUCCESS'
export const FETCH_DATA_FAILED = 'FETCH_DATA_FAILED'

export const getData = () => {
    return (dispatch) => {
        dispatch({
            type: FETCH_DATA_START
        })
        fetch("http://api.com", {
                credentials: "include",
                method: "POST",
                headers: {
                    'Accept': 'application/json',
                    'Content-Type': 'application/json'
                }
            })
            .then(res => res.json())
            .then((res) => {
                dispatch({
                    type: FETCH_DATA_SUCCESS,
                    payload: res
                })
            })
            .catch((err) => {
                console.log(err)
                dispatch({
                    type: FETCH_DATA_FAILED,
                    payload: 'error'
                })
            })
    }
}

这是我的减速器：

import { FETCH_DATA_START, FETCH_DATA_SUCCESS, FETCH_DATA_FAILED } from 'store/actions/getData'

let initialState = []

export default (state = initialState, action) => {
    switch (action.type) {
        case FETCH_DATA_START:
            return [...state]
        case FETCH_DATA_SUCCESS:
            return [...state, ...action.payload]    
        case FETCH_DATA_FAILED: 
            return [state]
        default:
            return state
    }
}

在我的组件中：

import React, {Component} from 'react'
import {connect} from 'react-redux';
import {bindActionCreators} from 'redux'
import {getData} from 'store/actions/getData'


class Ops extends Component {

    componentDidMount() {
        this.props.getData()
    }
    render() {
       console.log(this.props.dataOps)
       return(
           <div></div>
         )
    }
}


const mapStateToProps = state => ({dataOps: state.dataOps})

function mapDispatchToProps(dispatch) {
    return {
        getData: bindActionCreators(getData, dispatch)
    }
}

export default connect(mapStateToProps, mapDispatchToProps)(Ops)

Answer 1

选项1

在使用前检查减速器状态

选项2

 async componentDidMount(){
   //set loader true
   await this.props.getData;
   //set loader false
 }

Answer 2

您可以实现“加载”状态

import React, {Component} from 'react'
import {connect} from 'react-redux';
import {bindActionCreators} from 'redux'
import {getData} from 'store/actions/getData'


class Ops extends Component {

    state = {
      isLoading: true
    }

    componentDidMount() {        
        this.props.getData().then(res => res.json())
        .then((res) => {
            // Toggle state after promise completed
            this.setState({
              isLoading: false
            })  

            // Dispatch data
            dispatch({
                type: FETCH_DATA_SUCCESS,
                payload: res
            })
        })
        .catch((err) => {
            console.log(err)
            dispatch({
                type: FETCH_DATA_FAILED,
                payload: 'error'
            })
        })
    }
    }

    render() {     
      // If we're still loading data, show loading component
      if (this.state.isLoading) {
        return (<div>Loading...</div>);
      }

      console.log(this.props.dataOps)

      // Render with data
      return(
          <div>Loading completed!</div>
      )
    }
}


const mapStateToProps = state => ({dataOps: state.dataOps})

function mapDispatchToProps(dispatch) {
    return {
        getData: bindActionCreators(getData, dispatch)
    }
}

export default connect(mapStateToProps, mapDispatchToProps)(Ops)

编辑;返回承诺而不是已解决的数据；（不确定语法）

export const getData = () => {
    return (dispatch) => {
        dispatch({
            type: FETCH_DATA_START
        });

        return fetch("http://api.com", {
            credentials: "include",
            method: "POST",
            headers: {
                'Accept': 'application/json',
                'Content-Type': 'application/json'
            }
        })
    })
}

React-Redux在渲染组件之前等待获取结果

2 个答案: