react-saga

几个api

1. call和apply 执行异步请求操作 类似call的调用方法

yield call(Api.fetch, arg1, arg2...)
yield apply(this, Api.fetch, args)

2. put 执行action

yield put(action) //功能dispatch

3. take 订阅指定的action

yield take(action)
action的类型
1. * 
2. 字符串 匹配具体action
3. 数组
4. 函数

3.1 takeEvery 订阅一个action 绑定对应的回调函数

import { takeEvery } from `redux-saga`
function* fetchUser(action) {
  ...
}
function* watchFetchUser() {
  yield* takeEvery('USER_REQUESTED', fetchUser)
}

4. select 功能从store中取值, 是getState的包装

const count = select(state=>state.count)
//or
const count = getState().count