问Redux Thunk为什么我必须调用dispatch()两次？

EN

   /* actions.js */
import { store } from "../store.js";

store.dispatch(setStepPositionIndex());

export const SET_STEP_POSITION_INDEX = "SET_STEP_POSITION_INDEX";
export const setStepPositionIndex = () => {
  return (dispatch, getState) => {
    const newSteps = getState().goals.currentGoalSteps.map((stepObj, index) => {
      return { ...stepObj, positionIndex: index };
    });
    console.log("newSteps", newSteps);
    /* [{step: "Step3", positionIndex: 0}
      {step: "Step2", positionIndex: 1}
      {step: "Step1", positionIndex: 2}] */

    const actionObj = {
      type: SET_STEP_POSITION_INDEX,
      stepsArr: newSteps
    };
    // Unsuccessful alone ->
    // return actionObj

    // unsuccessful alone (removing dispatch() wrapper from setStepPositionIndex
    //->
    return dispatch(actionObj);
  };
};

/*Reducer.js*/

import * as actions from "../Actions/actions";
import { store } from "../store";
if (action.type === "SET_STEP_POSITION_INDEX") {
  return update(state, {
    currentGoalSteps: { $set: action.stepsArr }
  });
}

/*Store.js */
import { createStore, applyMiddleware, compose, combineReducers } from "redux";
import { ApolloClient } from "react-apollo";
import { createLogger } from "redux-logger";
import { reducer as formReducer } from "redux-form";
// import { client } from './index'
import thunk from "redux-thunk";
import * as Goal_Reducer from "./Reducers/Global_Reducer";

const logger = createLogger({
  collapsed: (getState, action, logEntry) => !logEntry.error,
  predicate: (getState, action) => !action.type.includes("@@redux-form")
});

const client = new ApolloClient();

const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;

export const store = createStore(
  combineReducers({
    goals: Goal_Reducer.goalReducer,
    apollo: client.reducer(),
    form: formReducer
  }),
  {}, //initial state
  composeEnhancers(applyMiddleware(client.middleware(), thunk, logger))
);