Javascript React Native Redux createStore错误：undefined不是对象（正在计算“action.type”）

我正在使用ReactNative的Redux，我想用reducer创建一个存储

下面是一个错误，指向reducer.js中函数switchToTab中的“switch action.type”行

undefined is not an object(evaluating 'action.type')

这是我的actions.js

export const SWITCH_TAB = 'switchTab'

export function switchTab(index) {

return {
    type: SWITCH_TAB,
    index: index
}

}

这是我的reducer.js

import { SWITCH_TAB } from './actions.js'

export function switchToTab(state = {}, action) {

switch (action.type) {//error point to this line

    case SWITCH_TAB:
        return Object.assign({}, ...state, {
            index: action.index
        });
    break;

    default:
        return state;
}

}

以下是createStore：

import { createStore } from 'redux';
import { switchToTab } from './reducer.js'

export default class MainPage extends Component {
    constructor(props) {
    super(props);
    this.state = {
        index:0
    };

    let store = createStore(switchToTab());
}

---

创建存储时，您不会调用reducer。createStore接受reducer函数作为其第一个参数

import { createStore } from 'redux';
import { switchToTab } from './reducer.js'

export default class MainPage extends Component {
    constructor(props) {
    super(props);
    this.state = {
        index:0
    };

    let store = createStore(switchToTab); // dont call this here, just pass it
}

---

发送操作的代码在哪里？看起来它是在调度一个空变量而不是actionnice，redux很棒，玩得开心！