Question

我的控制台输出正在生成正确的对象，然后在阵列图的末尾崩溃，我无法弄清楚undefined是什么。这是我的reducer，action和list实现。

减速器：

export default (state = INITIAL_STATE, action) => {
  switch (action.type) {
      case LOCATION_FETCH_SUCCESS:
          return action.payload;
      case POSTS_FETCH_FAIL:
        return state;
    default:
      return state;
  }
};

动作创建者：

 export const locationFetch = () => {
   const geoFire = new GeoFire(firebase.database().ref('/geoLocations'));
  var keys = [];
  var snaps = [];
  return (dispatch) => {
    navigator.geolocation.getCurrentPosition(
        (position) => {
          const currentLocation = [position.coords.latitude, position.coords.longitude];
          const radius = 0.5;
          const geoQuery = geoFire.query({ center: currentLocation, radius });
        var onKeyEntered = geoQuery.on("key_entered", (key) => {
            keys.push(key);
            console.log(key);
          });
        var onKeyReady = geoQuery.on('ready', () => {

          keys.map((key) => {

            firebase.database().ref('/posts').child(key).
                  once('value').then((snapshot) => {

                    snaps.push(snapshot.val());
                  //  console.log(snaps);
                    dispatch({ type: LOCATION_FETCH_SUCCESS, payload: snaps });


               });//.catch(() => postsFetchFail(dispatch));

             });
        });
   });
};
};

mapstatetoprops ：

const mapStateToProps = state => {

var objectArray = _.values(state.posts)
objectArray = _.flatten(objectArray);
//console.log(objectArray);
  objectArray.map((post) => {
    const { dishname,
      restaurant,
      category,
      likesCount
      } = post;
      console.log({ dishname , restaurant });
    return { dishname, restaurant };
});
};

export default connect(mapStateToProps, {locationFetch})(DshdList);

控制台的最后一个输出和我得到的错误消息如下：

10:43:33 PM
Object {
  "dishname": "shrimp bun",
  "restaurant": "momofuku ",
}
10:43:38 PM
▼mapStateToProps() in Connect(DshdList) must return a plain object. Instead received undefined

我不知道这出错了。

Answer 1

您必须从 mapStateToProps 函数返回对象，这是您缺少的。放置一个如下所示的退货声明

return objectArray.map（...）;

希望这会有所帮助。

错误：必须返回一个普通对象，而不是未定义

1 个答案: