javascript - 为什么当 redux 状态改变时 props.screenProps 会变成 undefined

Question

我正在尝试在 React Native 的自定义抽屉组件中显示按钮列表。这些按钮成功加载并呈现，但立即变为“未定义”，因此无法单击。当我单击按钮时，我收到的具体错误是“未定义不是对象(评估'props.screenProps.data.menu.items')”。在单击按钮之前，该应用程序运行良好，并且它们是可见的。

我尝试使用一些 JS 仅在按钮未定义时显示按钮，但按钮只是不显示，因为它们未定义。我的数据存储在 redux 中。

我的自定义抽屉:

const CustomDrawerComponent = (props) => (
    <Provider store={store}>
        <SafeAreaView style={{ flex: 1 }}>
        <View style={{height: 150, backgroundColor: 'white', alignItems: 'center', justifyContent: 'center'}}>
            <Text style={{marginTop: 50}}> Header Image / Logo</Text>
        </View>    
            <ScrollView>
            { //props.screenProps shows my list of buttons correctly, but clicking on them gives
            //the error of "undefined is not an object"
            //after initially rendering, they switch immediately to undefined
            //as proved by:  '''(props.screenProps.data.menu.items == undefined) &&''' 
            //doesn't show any buttons in the drawer
                props.screenProps.data.menu.items.map((_data) => { return( SideButtonClick(_data) ) })  
                }
            </ScrollView>
        </SafeAreaView>
    </Provider>
)
const SideButtonClick = (data) => {
    return(
        <Button title={data.title} key={data.title} 
            onPress = {() => store.dispatch({
            type: "CHANGE_CURRENT_DATA",
            payload: data }) } 
          />
    );
}

编辑:我的 reducer

export const reducer = (state = initialState, action) => {
    switch (action.type) {
        case "CHANGE_CURRENT_DATA": {
            state = {
                ...state,
                title: action.payload.title,
                link: action.payload.link,
                icon: action.payload.icon
            };
                console.log(action.payload);
                }
        case "CHANGE_DATA": {
            state = {
                ...state,
                data: action.payload
            };
             //console.log(action.payload);
        }
    }
    return state;
};

Answer 1

您的代码中缺少返回调用，因此您的 case 语句失败，并且 state.data 在 CHANGE_CURRENT_DATA 类型上被覆盖。更新您的 reducer 以在每个案例结束时返回state:

export const reducer = (state = initialState, action) => {
    switch (action.type) {
        case "CHANGE_CURRENT_DATA": {
            state = {
                ...state,
                title: action.payload.title,
                link: action.payload.link,
                icon: action.payload.icon
            };
                console.log(action.payload);
            return state;
                }
        case "CHANGE_DATA": {
            state = {
                ...state,
                data: action.payload
            };
             //console.log(action.payload);
           return state;
        }
    }
    return state;
};