简介

头部右侧之前有三个按键如下：

这是不合理的，我们应该根据登录态来做一个区别显示。未登录情况下显示login和购物车图标。已登录情况下显示用户名，logout，购物车图标。

本节有如下主要任务：

1. 将用户信息作为全局状态进行管理
2. 处理登入时的头部前端逻辑
3. 处理登出头时的部前端逻辑

1. 将用户信息作为全局状态进行管理

头部是公共组件，我们要求在所有引入头部组件页面中，都能根据用户态区别显示。那么我们需要将用户信息作为全局状态进行管理.
step1 引入vue的全局状态管理器vuex。

npm install vuex --save

step2 新建store目录如下：

user.js

const user = {
  state: {
    isLogin: false,
    userName: ''
  },
  mutations: {
    LOG_IN: (state, payload) => {
      state.isLogin = true
      state.userName = payload.userName
    },
    LOG_OUT: (state, payload) => {
      state.isLogin = false
      state.userName = ''
    }
  }
}

export default user

index.js

import Vue from 'vue'
import Vuex from 'vuex'
import user from './modules/user'

Vue.use(Vuex)

const store = new Vuex.Store({
  modules: {
    user
  }
})

export default store

step3 在main.js中引入store

// The Vue build version to load with the `import` command
// (runtime-only or standalone) has been set in webpack.base.conf with an alias.
import Vue from 'vue'
import App from './App'
import router from './router'
import store from './store'
import VueLazyLoad from 'vue-lazyload'

import './assets/css/base.css'
import './assets/css/login.css'
import './assets/css/product.css'

Vue.config.productionTip = false

Vue.use(VueLazyLoad, {
  loading: '../static/loading/loading-bars.svg',
  error: '../static/ok-2.png'
})

/* eslint-disable no-new */
new Vue({
  el: '#app',
  router,
  store,
  components: { App },
  template: '<App/>'
})

2. 处理登入时的头部前端逻辑

step1 修改PageHeader.vue逻辑如下

<template>
  <header class="header">
    <div class="navbar">
      <div class="navbar-left-container">
        <a href="/">
          <img class="navbar-brand-logo" src="../assets/logo.png"></a>
      </div>
      <div class="navbar-right-container" style="display: flex;">
        <div class="navbar-menu-container">
          <!--<a href="/" class="navbar-link">我的账户</a>-->
          <span class="navbar-link">{{user.userName}}</span>
          <a href="javascript:void(0)" class="navbar-link" v-if="!user.isLogin" @click="toPageLogin">Login</a>
          <a href="javascript:void(0)" class="navbar-link" v-else>Logout</a>
          <div class="navbar-cart-container">
            <span class="navbar-cart-count"></span>
            <a class="navbar-link navbar-cart-link" href="/#/cart">
              <svg class="navbar-cart-logo">
                <symbol id="icon-cart" viewBox="0 0 38 32">
                  <title>cart</title>
                  <path class="path1"
                        d="M37.759 0h-4.133c-0.733 0.004-1.337 0.549-1.434 1.255l-0.546 4.342c-0.081 0.484-0.496 0.849-0.997 0.849-0.005 0-0.009-0-0.014-0h-27.604c-0.003 0-0.007-0-0.011-0-1.674 0-3.031 1.357-3.031 3.031 0 0.34 0.056 0.666 0.159 0.971l2.52 8.062c0.385 1.194 1.486 2.043 2.785 2.043 0.126 0 0.25-0.008 0.372-0.023l22.983 0.002c0.515 0.131 0.626 0.768 0.626 1.283 0.005 0.044 0.009 0.095 0.009 0.146 0 0.501-0.294 0.933-0.718 1.134l-22.439 0.003c-0.354 0-0.642 0.287-0.642 0.642s0.287 0.642 0.642 0.642h22.745l0.131-0.071c0.919-0.392 1.551-1.287 1.551-2.33 0-0.058-0.002-0.116-0.006-0.173 0.021-0.108 0.033-0.24 0.033-0.376 0-1.072-0.732-1.973-1.724-2.23l-23.357-0.004c-0.063 0.008-0.135 0.013-0.209 0.013-0.719 0-1.332-0.455-1.566-1.093l-2.53-8.095c-0.048-0.154-0.076-0.332-0.076-0.515 0-0.973 0.782-1.764 1.752-1.778h27.657c1.159-0.004 2.112-0.883 2.232-2.011l0.547-4.345c0.010-0.083 0.078-0.147 0.161-0.152l4.133-0c0.354 0 0.642-0.287 0.642-0.642s-0.287-0.642-0.642-0.642z"></path>
                  <path class="path2"
                        d="M31.323 9.69c-0.022-0.003-0.048-0.004-0.074-0.004-0.328 0-0.598 0.248-0.633 0.567l-0.809 7.268c-0.003 0.022-0.004 0.048-0.004 0.074 0 0.328 0.248 0.598 0.567 0.633l0.074 0c0.001 0 0.003 0 0.004 0 0.327 0 0.596-0.246 0.632-0.563l0.809-7.268c0.003-0.022 0.004-0.048 0.004-0.074 0-0.328-0.248-0.598-0.567-0.633z"></path>
                  <path class="path3"
                        d="M27.514 25.594c-1.769 0-3.203 1.434-3.203 3.203s1.434 3.203 3.203 3.203c1.769 0 3.203-1.434 3.203-3.203s-1.434-3.203-3.203-3.203zM27.514 30.717c-1.060 0-1.92-0.86-1.92-1.92s0.86-1.92 1.92-1.92c1.060 0 1.92 0.86 1.92 1.92s-0.86 1.92-1.92 1.92z"></path>
                  <path class="path4"
                        d="M9.599 25.594c-1.769 0-3.203 1.434-3.203 3.203s1.434 3.203 3.203 3.203c1.769 0 3.203-1.434 3.203-3.203s-1.434-3.203-3.203-3.203zM9.599 30.717c-1.060 0-1.92-0.86-1.92-1.92s0.86-1.92 1.92-1.92c1.060 0 1.92 0.86 1.92 1.92s-0.86 1.92-1.92 1.92z"></path>
                </symbol>
                <use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-cart"></use>
              </svg>
            </a>
          </div>
        </div>
      </div>
    </div>
  </header>
</template>

<script>
import { mapState } from 'vuex'

export default {
  computed: {
    ...mapState([
      'user'
    ])
  },
  methods: {
    // 跳转登录页
    toPageLogin () {
      this.$router.push({ path: '/login', query: { redirect: this.$route.fullPath } })
    }
  }
}
</script>

step3 修改Login.vue
改动如下逻辑：

axios.post('/api/users/login', queryObj).then(res => {
        let data = (res && res.data) || {}
        if (data.code === '000') {
          let result = data.result || {}
          this.$store.commit('LOG_IN', {userName: result.userName})
          if (this.$route.query.redirect) {
            this.$router.push(this.$route.query.redirect)
          } else {
            this.$router.push('/')
          }
        } else {
          alert(`err:${data.msg || '系统错误'}`)
        }
      })

此时尝试运行，能正常跳转到登录页，但是输入第一遍用户名和密码时，并没有跳转，第二遍才跳转。因为这里button在form内，默认会执行submit。可以简单地在该button中添加'type= button'，也可以将button挪到form外，不过此时userName和userPwd为空不再有提示，需要我们补充提示逻辑。重新修改Login.vue如下：

<template>
  <div class="login">
    <div class="logo">
      <h1>weleome to six-tao</h1>
    </div>
    <form action="">
      <div class="item">
        <label for="userName">账号：</label>
        <input type="text" placeholder="Username" v-model="userName" id="userName"/>
      </div>
      <div class="item">
        <label for="userPwd">密码：</label>
        <input type="userPwd" placeholder="userPwd" v-model="userPwd" id="userPwd"/>
      </div>
      <div class="item err-tip" v-show="errTip">
        <label>提示：</label>
        <span>{{errTip}}</span>
      </div>
    </form>
    <div class="btn-wraper">
      <button id="loginButton" @click="login">登录</button>
    </div>
  </div>
</template>

<script>
import axios from 'axios'

export default {
  data () {
    return {
      userName: '',
      userPwd: '',
      errTip: ''
    }
  },
  methods: {
    login () {
      if (!this.userName || !this.userPwd) {
        this.errTip = '用户名和密码不能为空'
        return
      }
      this.errTip = ''
      let queryObj = {
        userName: this.userName,
        userPwd: this.userPwd
      }
      axios.post('/api/users/login', queryObj).then(res => {
        let data = (res && res.data) || {}
        if (data.code === '000') {
          let result = data.result || {}
          this.$store.commit('LOG_IN', {userName: result.userName})
          if (this.$route.query.redirect) {
            this.$router.push(this.$route.query.redirect)
          } else {
            this.$router.push('/')
          }
        } else {
          alert(`err:${data.msg || '系统错误'}`)
        }
      })
    }
  }
}
</script>

<style scoped>
  .login {
    font-size: 12px;
    position: fixed;
    width: 300px;
    height: 240px;
    background-color: lightcyan;
    border-radius: 10px;
    padding: 10px 20px 10px 10px;
    margin-top: -120px;
    margin-left: -150px;
    top: 50%;
    left: 50%;
  }
  .item {
    display: flex;
    align-items: center;
    margin-top: 20px
  }
  .item label {
    width: 60px;
    font-size: 1.2em;
  }
  .item input {
    flex: 1;
    height: 40px;
    line-height: 40px;
  }
  .btn-wraper {
    display: flex;
    justify-content: center;
  }
  .err-tip {
    margin-top: 5px;
    color: red;
  }
  #loginButton {
    width: 100px;
    color: #85592e;
    margin-left: auto;
    margin-right: auto;
    margin-top: 30px;
    background: yellow;
    border-radius: 5px;
    border: 1px solid gray;
    font-size: 1.2em;
  }
  .logo {
    text-align: center;
  }
</style>

此时，我们再来运行一遍：

3. 处理登出时的头部前端逻辑

修改PageHeader.vue以下两处：

<a href="javascript:void(0)" class="navbar-link" v-else @click="logout">Logout</a>

logout () {
      this.$store.commit('LOG_OUT')
}

总结

这一节我们从前端角度完成了登入登出的头部前端逻辑。但是仍然还有一些问题，下一节我们继续来完善。
提交一下代码：
six-tao

git status
git diff
git add .
git status
git commit -am 'head logic changes to fit login'
git push