要从reactjs中的同一个减速机返回不同的值吗

我正在使用action/index文件中的action creator define从API获取数据。 有人能告诉我为什么state.all.concat没有定义吗

错误看起来像这样

import {FETCH_OBSERVATION} from '../actions/index';
import {DELETE_OBSERVATION} from '../actions/index';

export default function(state={all:[],count:null},action){
  switch (action.type) {
    case FETCH_OBSERVATION:
    console.log("data for fetch observationCount",action.payload.data.model.observationInstanceList);

     return{
       all:state.all.concat(action.payload.data.model.observationInstanceList),
       count:action.payload.data.model.observationCount
     }
    case DELETE_OBSERVATION:
    return state.all=[];
    default:
    return state

  }
  return state;
}

Cannot read property 'concat' of undefined
at ./src/reducers/reducer_observation.js.__webpack_exports__.a (reducer_observation.js:10)
at combination (combineReducers.js:120)
at dispatch (createStore.js:165)
at redux-logger.js:1
at index.js:28
at dispatch (applyMiddleware.js:35)
at action.payload.then._extends.payload (index.js:25)
at <anonymous>

---

好的，如果你想让上面的函数工作，那么就这样做

import { combineReducers } from 'redux';
import SpeciesChartReducer from './reducer_chart_data';
import ObservationReducer from './reducer_observation';
import TaxonReducer from './reducer_taxon_list';
import  UserGroupNames from './reducer_fetch_userGroup';
import  UserGroupObservations from './reducer_fetch_groupobservations';
import  HomeTotalCount from './reducer_home_total_count';

const rootReducer = combineReducers({
  Observation:ObservationReducer,
  ChartData:SpeciesChartReducer,
  treeData:TaxonReducer,
  UserGroupNames:UserGroupNames,
  UserGroupObservations:UserGroupObservations,
  HomeTotalCount:HomeTotalCount
});

export default rootReducer;

---

`

你所说的console.log到底是什么意思？这是：action.payload.data.model.ObservationStanceList？，返回状态为.all=[]；你改变了状态，也返回了不同形状的状态。我很确定那不是你想做的。您可能希望再次返回默认状态。最好将其提取到常量。例如：const DEFAULT_STATE={all:[]，count:null}；在reducer外部和内部：functionstate=DEFAULT_STATE，action{和更高版本：case DELETE_OBSERVATION:return DEFAULT_STATE；。实际上，我正在观察页面上实现过滤器。因此，一旦应用新过滤器，我想删除显示的观察，并加载新的观察，这就是为什么我在执行此状态后删除上一个观察。全部：[]。如果你有任何想法，请分享考虑上述场景。我正在从事的项目是开源的，你可以在这里查看功能网站。上面的页面是我想要实现的。这与你最终尝试实现的目标并不相关，变异和返回不同的状态形状是简单的错误做法。参考nce:…这就是我在执行此状态后删除上一个的原因。all:[]但这就是问题所在。您1通过改变状态来删除它，错误。2您返回的状态形状不同。状态现在是表达式状态的结果。all=[]；这是一个普通数组，不好。您要做的是返回一个新状态，该状态具有正确的形状，表示相同的属性。如果这样做，您会发现它与默认状态非常相似。因此，我建议提取它。

import {FETCH_OBSERVATION} from '../actions/index';
import {DELETE_OBSERVATION} from '../actions/index';
const DEFAULT_STATE={all:[],count:null}
export default function(state=DEFAULT_STATE,action){
  switch (action.type) {
    case FETCH_OBSERVATION:
     return{
       all:state.all.concat(action.payload.data.model.observationInstanceList),
       count:action.payload.data.model.observationCount
     }
    case DELETE_OBSERVATION:
    return DEFAULT_STATE;
    default:
    return DEFAULT_STATE

  }
  return DEFAULT_STATE;
}