如何写入来自 Firebase 的数据以快速存储？

首先，我正在使用 React Native。我正在从 Firebase 获取数据并希望快速写入存储（通过 Redux）。但这不起作用。您可以在下面找到我的所有代码：

功能：

async getTumData (uid) {

    const {selectedGroupDetail, getSelectedGroupDetail} = this.props;
    var yeniGrupDetayi = {};
    await firebase.database().ref("/groups/"+uid).once('value').then(
      function(snapshot){
        yeniGrupDetayi = {...snapshot.val(), uid: uid};
      }).catch(e => console.log(e.message));

      console.log("FONKSIYON ICERISINDEKI ITEM ==>", yeniGrupDetayi);
      this.props.getSelectedGroupDetail(yeniGrupDetayi);
      console.log("ACTION'DAN GELEN ITEM ===>", selectedGroupDetail);

  }

Action:

export const getSelectedGroupDetail = (yeniGrupDetayi) => {
  return {
    type: GET_SELECTED_GROUP_DETAIL,
    payload: yeniGrupDetayi
  }
};

Reducer:

case GET_SELECTED_GROUP_DETAIL:
      return { ...state, selectedGroupDetail: action.payload}

Çıktı:

FONKSIYON ICERISINDEKI ITEM ==> {admin: {…}, groupDescription: "Yaygın inancın tersine, Lorem Ipsum rastgele sözcü…erini incelediğinde kesin bir kaynağa ulaşmıştır.", groupName: "İnsan Kaynakları", groupProfilePic: "", members: {…}, …}

ACTION'DAN GELEN ITEM ===> {}

我的页面中有一个 FlatList，我在 FlatList 的 renderItem 中定义了一个按钮。当我点击这个按钮时，getTumData()功能正在运行。

当我第一次点击这个按钮时，selectedGroupDetail is null。第二次，它显示以前的数据。

如何快速地将数据写入存储？

Thanks,

事情是： - 您在代码中同时使用了 async/await 和 then/catch 。 - 您在异步代码解析之前调用 getSelectedGroupDetail。

快速解决方案

getTumData =  (uid) => {

    const {selectedGroupDetail, getSelectedGroupDetail} = this.props;
    var yeniGrupDetayi = {};
    firebase.database().ref("/groups/"+uid).once('value').then(
     (snapshot) => {
        yeniGrupDetayi = {...snapshot.val(), uid: uid};
        this.props.getSelectedGroupDetail(yeniGrupDetayi);
      }).catch(e => console.log(e.message));   
  };

更好的解决方案：

第一：使用 Redux-Thunk 中间件。 第二：将你的异步代码移到你的动作创建者中：我的意思是这个

async getTumData (uid) {

    const {selectedGroupDetail, getSelectedGroupDetail} = this.props;
    var yeniGrupDetayi = {};
    await firebase.database().ref("/groups/"+uid).once('value').then(
      function(snapshot){
        yeniGrupDetayi = {...snapshot.val(), uid: uid};
      }).catch(e => console.log(e.message));

      console.log("FONKSIYON ICERISINDEKI ITEM ==>", yeniGrupDetayi);
      this.props.getSelectedGroupDetail(yeniGrupDetayi);
      console.log("ACTION'DAN GELEN ITEM ===>", selectedGroupDetail);

  }

第三：在您选择的组详细信息解析之前，您的减速器应该有另一条数据作为时间间隙的指示器：

// reducer initial state:
const INITIAL_STATE = { error: '', loading: false, selectedGroupDetail: null }

第四：在你的动作创建器中，你应该调度 3 个动作： ACTION_NAME_START // 这应该只在你的reducer中将loading设置为true。 ACTION_NAME_SUCCESS // 将loading设置为false，并将selectedGroupDetail设置为返回的新集合 ACTION_NAME_FAIL // 如果操作失败设置错误

第五：你的 React 组件应该显示一个加载指示器（旋转器或其他东西），并且可能在加载状态期间禁用 FlatList 按钮。

// Action creator
export const myAction = () => (dispatch) => {
  dispatch({ type: ACTION_NAME_START });
  firebase.database().ref("/groups/"+uid).once('value').then(
  function(snapshot){
    yeniGrupDetayi = {...snapshot.val(), uid: uid};
    dispatch({ type: ACTION_NAME_SUCCESS, payload: yeniGrupDetayi  });

  }).catch(e => {
  dispatch({ type: ACTION_NAME_FAIL, payload: e.message });
});

};


// Reducer
const INITIAL_STATE = {
  loading: false,
  error: '',
  data: null,
};

export default (state = INITIAL_STATE, { type, payload }) => {
  switch (type) {
    case ACTION_NAME_START:
      return {
        ...state,
        error: '',
        loading: true,
        data: null,
      };

    case ACTION_NAME_SUCCESS:
      return {
        ...state,
        error: '',
        loading: false,
        data: payload,
      };

    case ACTION_NAME_FAIL:
      return {
        ...state,
        error: payload,
        loading: false,
        data: null,
      };

    default:
      return state;
  }
};