看到一个项目中引入的是 import fetch from 'isomorphic-fetch';

然后在定义action—type时，写的：

export const FETCH_RUNS = 'FETCH_RUNS';
export const FETCH_RUNS_PENDING = 'FETCH_RUNS_PENDING';
export const FETCH_RUNS_FULFILLED = 'FETCH_RUNS_FULFILLED';
export const FETCH_RUNS_REJECTED = 'FETCH_RUNS_REJECTED';

加了三种状态pending，fulfilled，rejected

action中只写了type: FETCH_RUNS的：

import {fetchRuns} from '../../services/RunService';
const fetchRunsAction = (req) => ({
  type: FETCH_RUNS,
  payload: fetchRuns(req)
});
export {
  fetchRunsAction as fetchRuns
}

而在reducer中对三种状态的action都做了处理：

import {
  FETCH_RUNS_FULFILLED,
  FETCH_RUNS_PENDING,
  FETCH_RUNS_REJECTED
} from '../actions/runActions';


// INITIALIZE STATE

const initialState = {
  runs: null,
  fetched: false,
  fetching: false,
  failed: false
};


// REDUCER

export const FetchRunsReducer = (state = initialState, action) => {
  switch (action.type) {
    case FETCH_RUNS_PENDING:
      return {
        ...state,
        fetching: true,
        fetched: false,
        failed: false
      };
    case FETCH_RUNS_FULFILLED:
      return {
        ...state,
        runs: action.payload,
        fetching: false,
        fetched: true,
        failed: false
      };
    case FETCH_RUNS_REJECTED:
      return {
        ...state,
        runs: null,
        fetching: false,
        fetched: false,
        failed: true
      };
    default:
      return state;
  }
};

在组件中：

...
const mapStateToProps = state => {
  const {fetched, fetching, runs} = state.runs;

  return {
    fetched,
    fetching,
    runs
  };
};

const mapDispatchToProps = dispatch => {
  return bindActionCreators({fetchRuns}, dispatch);
};

再贴一下RunService中代码

import {fetchJSON} from '../utils/Fetch';

// SERVICES

export const fetchRuns = fetchJSON('/run/list');

Fetch中代码：

import fetch from 'isomorphic-fetch';

// INITIALIZATION

export const baseURL = '';
const defaultConfig = {
  ...
};

// SERVICES

export const fetchJSON = (route, patchConfig, target) => (params) => {
  const body = JSON.stringify(params || {});
  const config = { ...defaultConfig, ...(patchConfig || {}) };
  const data = config.method === 'POST' ? {...config, body} : config;
  const url = (target || baseURL) + route;
  return new Promise((resolve, reject) => {
    fetch(url, data).then((response) => {
      if (!response.ok) {
        reject(response);
      } else {
        return response.json();
      }
    }).then(json => {
      if (json.success) {
        resolve(json.result);
      } else {
        reject(json);
      }
    }).catch(error => {
      return reject(error);
    });
  });
};

现在我的疑惑点在——什么时候触发了FETCH_RUNS_PENDING，FETCH_RUNS_FULFILLED，FETCH_RUNS_REJECTED这三个状态；在promise是有三个状态，自动触发，但是程序如何跳到代码中写的这三个action名字FETCH_RUNS_PENDING，FETCH_RUNS_FULFILLED，FETCH_RUNS_REJECTED；我想是不是某个封装的地方给action名字自动后面添加了PENDING、FULFILLED，REJECTED然后在触发此action的时候后自动触发这几个状态的action。那么请问在哪个里面进行了封装呢？代码中没有找到啊，是不是react，redux某个里面封装的？求助