為什么在redux狀態更改時props.screenProps變得不確定

Question

我正在嘗試在React Native的自定義抽屜組件中顯示按鈕列表。 按鈕成功加載和渲染，但立即變為“未定義”，因此不可單擊。 當我單擊按鈕時，我得到的特定錯誤是“ undefined不是對象（正在評估'props.screenProps.data.menu.items'）”。 在單擊按鈕之前，該應用程序可以正常運行，並且可以查看它們。

我嘗試使用一些JS僅在按鈕未定義的情況下顯示按鈕，但是按鈕卻未顯示，因為它們未定義。 我的數據存儲在redux中。

我的自定義抽屜：

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 }) } 
          />
    );
}

編輯：我的減速機

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

您在代碼中缺少返回調用，因此您的case語句不state.data ，state.data在CHANGE_CURRENT_DATA類型上變得不知所措。 在每種情況下，將減速器更新為返回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;
};