action创建函数

//action的type应该用常量来命名
const ADD_TYPE = "ADD"
const MINUS_TYPE = "MINUS"
const CITY_TYPE = "CHOOSECITY"

//操作counter的action
export function add(step) {
    return {
        type: ADD_TYPE,
        step: step
    }
}
export function minus() {
    return {
        type: MINUS_TYPE
    }
}

//使用
button onClick={() => { store.dispatch(add(30)) }}>点我加</button>
<button onClick={() => { store.dispatch(minus()) }}>点我减</button>

多个reducer合并

//先引入combineReducers
import { combineReducers } from 'redux'
//再将需要合并的reducer文件引入
import city from './city'
import counter from './counter'

//将city和counter两个reducers合并在一起
//现在city这个reducer专门用来管理city数据
//counter这个reducer专门用来管理counter的数据
export default combineReducers({
    city,
    count:counter
})

/*
现在合并后的数据就变成这样了
{
  city:"无锡",
  count:0
}
*/

//3.引入合并后reducers
import reducer from './reducers'
//使用合并后的reducer来创建store
let store = createStore(reducer)