redux-saga实现redux异步方法调用

之前说过一篇通过redux-thunk实现redux的异步调用,今天我们通过代码来看看这两个在实现上的区别.
redux-saga可以处理各种复杂的异步操作，redux-thunk适⽤于简单的异步操作场景
redux-saga使用generator解决异步问题，使⽤同步方式编写异步代码，解决回调地域问题
redux-thunk可以接受function类型的action，而redux-saga则 是纯对象action的解决⽅案
我们来修改上一篇中的路由守卫的代码,之前是使用redux-thunk实现的异步操作,今天采用redux-saga对他进行改造.在此之前大家需要先了解generator函数.

首先安装redux-saga

npm install redux-saga -S     or
cnpm install redux-saga -S   or
yarn add redux-saga

安装成功后启动项目开始改造我们的代码
我们在src/store下面创建一个新的saga.js文件来编写我们的saga代码.

src/store/login-redux.js

const initState = {
    login: false,
    loading: false,
    errmsg: ""
}
export const loginReducer = (state=initState, action) => {
    switch(action.type){
        case "nowlogin":
            return {
                login: false,
                loading: true,
                errmsg: ""
            }
        case "haslogin":
            return {
                login: true,
                loading: false,
                errmsg: ""
            }
        case "loginfail":
            return {
                login: false,
                loading: false,
                errmsg: action.message
            }
        default :
            return state
    }
}
//这个文件没有太大的变化,新添加一个触发saga的action文件,并导出
function login (name){
    return {type: "LOGIN_REQUEST", name}
}

export {login}

src/store/saga.js

//call用来调用异步方法,put派发reduer的action以及获取的值, takeEvery监听触发saga的事件
import { call, put, takeEvery } from "redux-saga/effects"
//模拟一个异步方法
const user = {
    login(name){
        return new Promise((reslove, reject) => {
            setTimeout(()=>{
              //当用户输入的值等于tom则登录成功,否则失败
                if(name == "tom"){
                    reslove({name: "tom", age: 20})
                }else{
                    reject("用户名或密码有误")
                }
            },1000)
        })
    }
}
//执行异步方法并派发action,因为这个过程可能会报错,用try,catch来捕获
function *login(action){
    try{
        yield put({type: "nowlogin"})
        const res = yield call(user.login, action.name)
        yield put({type: "haslogin", res})
    }catch (message){
        yield put({type: "loginfail", message})
    }
 }
//监听触发saga事件,并执行上面的generator   login函数
function* mysaga(){
    yield takeEvery("LOGIN_REQUEST",login)
}

export default mysaga

src/store/index.js

import { createStore, applyMiddleware, combineReducers } from "redux"
import logger from "redux-logger"
import {loginReducer} from "./login-redux"
import {countRedux} from "./count-redux"
import createSagaMiddleware from "redux-saga"
import saga from "./saga"

const mid = createSagaMiddleware();
const store = createStore(combineReducers({
    count: countRedux,
    login: loginReducer
}), applyMiddleware(logger, mid))
mid.run(saga)

export default store;

src/routerdemo.js

//其他代码和上一篇一样,我们在这只展示修改的地方
import React,{ useState } from "react"
import { BrowserRouter as Router, Route, Link, Redirect, Switch } from "react-router-dom"
import { connect } from "react-redux"
import {login} from "./store/login-redux"//引入触发saga的action
//修改登录组件
const Login = connect(state => (
{isLogin: state.login.login, 
loading: state.login.loading,
 error: state.login.errmsg}//加入了登录失败的错误信息
),{login})(
    function ({location, isLogin, loading, login, error}){
        const fromUrl = location.state&&location.state.jumpUrl || "/";
        if(isLogin){
            return <Redirect to={fromUrl}></Redirect>
        }
        const [name, setname] = useState("");
        return(
            <div>
              //将用户输入的值存入状态中
                <input type="text" onInput={(e) => setname(e.target.value)}/><br />
                <button onClick={() => login(name)}>{loading? "登录中..." : "登陆"}</button>
                {error && <p style={{color: "red"}}>{error}</p>}//如果失败,展示错误信息
            </div>
        )
    }
)

查看页面

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