React-native return 中的 UseSelector 未定义但 redux 中的变量得到更新

Question

我尝试使用 UseSelector 在 redux 中获取数据，但它总是返回未定义的，但是当我尝试记录 console.log 我想在 redux 中获取的变量时，它得到了更新，但是当我尝试控制台记录它返回的 useSelector undefined

代码 Redux :

export const EXCHAHNGETOSECOND = 'EXCHANGETOSECOND'

export const exchangetosecwork = (hour,minute,second) =>({
    type:EXCHAHNGETOSECOND,
    payloadhourwork : hour,
    payloadminutework : minute,
    payloadsecondwork : second
})

let initialState ={
    resultWorkinSecond : 0
}

export const mainReducer = (state=initialState, action) =>{
    switch (action.type) {
        case EXCHAHNGETOSECOND:
            const hourTosecond = action.payloadhourwork * 3600
            const minuteTosecond = action.payloadminutework * 60
            const res = hourTosecond+minuteTosecond+action.payloadsecondwork
            state.resultWorkinSecond = res
            console.log(state.resultWorkinSecond);
            return state.resultWorkinSecond
        default:
            return state
    }
}

export default mainReducer

存储 redux :

import { createStore } from "redux";
import mainReducer from "./redux";
import AsyncStorage from '@react-native-async-storage/async-storage';
import { persistStore, persistReducer } from 'redux-persist'


const persistConfig={
    key:'root',
    storage:AsyncStorage,
};

const persistedReducer = persistReducer(persistConfig,mainReducer)

export default() => {
    let store = createStore(persistedReducer)
    let persistor = persistStore(store)
    return{ store, persistor }
}

myConsole 日志测试：

 const resWorkinSec = useSelector((state)=>state.resultWorkinSecond)
    
    <Pressable onPress={()=>{
                            dispatch(exchangetosecwork(hour,minute,second))
                            console.log(resWorkinSec)
                        }}>

[控制台日志结果1

Answer 1

您的减速器有多个错误：

它做一个赋值，改变状态。这在旧版 Redux reducer 中是不允许的，但仅在使用 createSlice
return state.resultWorkinSecond 然后甚至改变完整的状态结构。

正确的遗留 Redux 代码如下所示：

export const mainReducer = (state=initialState, action) =>{
    switch (action.type) {
        case EXCHAHNGETOSECOND:
            const hourTosecond = action.payloadhourwork * 3600
            const minuteTosecond = action.payloadminutework * 60
            const res = hourTosecond+minuteTosecond+action.payloadsecondwork
            return { ...state, resultWorkinSecond: res }
        default:
            return state
    }
}

综上所述，这是我们自 2019 年以来不再推荐的旧 Redux 风格。它更复杂，并且 error-prone。大约是现代 Redux 代码的 4 倍。现代 Redux 不使用 switch..case reducers，ACTION_TYPES，不可变的 reducer 逻辑（就像你需要在这里做的那样），createStore 等等。

我强烈建议您暂时放下手头的工作，仔细阅读 official Redux tutorial。

React-native return 中的 UseSelector 未定义但 redux 中的变量得到更新

UseSelector in react-native return undefined but variable in redux get updated

javascript

react-native

redux