前端【VUE】06-vue【组件组成】【组件通信【父传子、子传父、非父子传递】】【进阶语法【.sync修饰符、v-model原理、$refs、自定义指令、Vue异步更新、$nextTick】】【子组件修改父组件的值】

一、组件的三大组成部分(结构/样式/逻辑)

组件的三大组成部分

　　

组件的样式冲突scoped

　　

1、components目录下

components/BaseOne.vue

<template>
  <div class="base-one">
    BaseOne
  </div>
</template>

<script>
export default {

}
</script>

<style scoped>
/* 
  1.style中的样式 默认是作用到全局的
  2.加上scoped可以让样式变成局部样式

  组件都应该有独立的样式，推荐加scoped（原理）
  -----------------------------------------------------
  scoped原理：
  1.给当前组件模板的所有元素，都会添加上一个自定义属性
  data-v-hash值
  data-v-5f6a9d56  用于区分开不通的组件
  2.css选择器后面，被自动处理，添加上了属性选择器
  div[data-v-5f6a9d56]
*/
div{
  border: 3px solid blue;
  margin: 30px;
}
</style>

components/BaseTwo.vue

<template>
  <div class="base-one">
    BaseTwo
  </div>
</template>

<script>
export default {

}
</script>

<style scoped>
 div{
  border: 3px solid red;
  margin: 30px;
 }
</style>

2、根组件App.vue

<template>
  <div id="app">
    <BaseOne></BaseOne>
    <BaseTwo></BaseTwo>
  </div>
</template>

<script>
import BaseOne from './components/BaseOne'
import BaseTwo from './components/BaseTwo'
export default {
  name: 'App',
  components: {
    BaseOne,
    BaseTwo
  }
}
</script>

data 是一个函数

　　

 1、components/BaseCount.vue

<template>
  <div class="base-count">
    <button @click="count--">-</button>
    <span>{{ count }}</span>
    <button @click="count++">+</button>
  </div>
</template>

<script>
export default {
  data: function () {
    return {
      count: 100,
    }
  },
}
</script>

<style>
.base-count {
  margin: 20px;
}
</style>

2、根组件App.vue

<template>
  <div class="app">
    <!-- 使用导入的组件, 每个组件都维护了自己的data，加减都是只影响自己组件内的data数据 -->
    <baseCount></baseCount>
    <baseCount></baseCount>
    <baseCount></baseCount>
  </div>
</template>

<script>
import baseCount from './components/BaseCount'
export default {
  components: {
    baseCount,
  },
}
</script>

<style>
</style>

组件三大组成部分的注意点

　　1. 结构：有且只能一个根元素
　　2. 样式：默认全局样式，加上scoped局部样式
　　3. 逻辑：data是一个函数，保证数据独立。

 

二、组件通信

什么是组件通信

　　

 不同的组件关系和组件通信方案分类

　　

 组件通信解决方案

　　

父子通信流程图

　　

 父组件传递数据到子组件

　　父组件通过props将数据传递给子组件

　　

1、components/Son.vue

<template>
  <div class="son" style="border:3px solid #000;margin:10px">
    <!-- 3.通过插值表达式 直接使用props的值 -->
    我是Son组件 {{title}}
  </div>
</template>

<script>
export default {
  name: 'Son-Child',
  // 2.通过props来接受
  props:['title']
}
</script>
<style>
</style>

2、根组件App.vue

<template>
  <div class="app" style="border: 3px solid #000; margin: 10px">
    我是APP组件
    <!-- 1.给组件标签，添加属性方式 赋值   :title 中的title是自定义的属性名称, 需要与子组件中的props中保持一致   而:title="myTitle"中的myTitle是data中的变量 -->
    <Son :title="myTitle"></Son>
  </div>
</template>

<script>
import Son from './components/Son.vue'
export default {
  name: 'App',
  data() {
    return {
      myTitle: '学前端，就来黑马程序员',
    }
  },
  components: { // 使用导入的组件
    Son,
  },
}
</script>

<style>
</style>

子组件传递数据给父组件

　　子组件利用$emit通知父组件，进行修改更新

　　

 1、components/Son.vue

<template>
  <div class="son" style="border: 3px solid #000; margin: 10px">
    我是Son组件 {{ title }}
    <!-- 方式1 -->
    <button @click="changeFn">修改title</button>
    <!-- 方式2：行内式 -->
    <button @click="$emit('changTitle','我是传递的参数')">修改title</button>
  </div>
</template>

<script>
export default {
  name: 'Son-Child',
  props: ['title'], // 接收父组件传的值
  methods: {
    changeFn() {
      // 通过this.$emit() 向父组件发送通知
      // changTitle通知父组件的函数, 
      this.$emit('changTitle','我是传递的参数')
    },
  },
}
</script>
<style>
</style>

2、根组件App.vue

<template>
  <div class="app" style="border: 3px solid #000; margin: 10px">
    我是APP组件
    <!-- 2.父组件对子组件的消息进行监听 -->
    <!-- @changTitle 此处的changTitle必须与子组件调用的$emit()第一个参数保持一致 监听事件 -->
    <Son :title="myTitle" @changTitle="handleChange"></Son>
  </div>
</template>

<script>
import Son from './components/Son.vue'
export default {
  name: 'App',
  data() {
    return {
      myTitle: '学前端',
    }
  },
  components: {
    Son,
  },
  methods: {
    // 3.提供处理函数，提供逻辑
    handleChange(newTitle) {
      this.myTitle = newTitle
    },
  },
}
</script>
<style>
</style>

 

什么是prop

　　

props传值

 1、components/UserInfo.vue

<template>
  <div class="userinfo">
    <h3>我是个人信息组件</h3>
    <div>姓名：{{username}}</div>
    <div>年龄：{{age}}</div>
    <div>是否单身：{{isSingle}}</div>
    <div>座驾：{{car.brand}}</div>
    <div>兴趣爱好：{{hobby.join('、')}}</div>
  </div>
</template>

<script>
export default {
  props:['username','age','isSingle','car','hobby']
}
</script>

<style>
.userinfo {
  width: 300px;
  border: 3px solid #000;
  padding: 20px;
}
.userinfo > div {
  margin: 20px 10px;
}
</style>

2、根组件App.vue

<template>
  <div class="app">
    <UserInfo
      :username="username"
      :age="age"
      :isSingle="isSingle"
      :car="car"
      :hobby="hobby"
    ></UserInfo>
  </div>
</template>

<script>
import UserInfo from './components/UserInfo.vue'
export default {
  data() {
    return {
      username: '小帅',
      age: 28,
      isSingle: true,
      car: {
        brand: '宝马',
      },
      hobby: ['篮球', '足球', '羽毛球'],
    }
  },
  components: {
    UserInfo,
  },
}
</script>
<style>
</style>

props校验

　　

 1、components/BaseProgress.vue

<template>
  <div class="base-progress">
    <div class="inner" :style="{ width: w + '%' }">
      <span>{{ w }}%</span>
    </div>
  </div>
</template>

<script>
export default {
  // 1.基础写法（类型校验）
  // props: {
  //   w: Number,
  // },

  // 2.完整写法（类型、默认值、非空、自定义校验）
  props: {
    w: {
      type: Number,
      required: true,
      default: 0,
      validator(val) {
        // console.log(val)
        if (val >= 100 || val <= 0) {
          console.error('传入的范围必须是0-100之间')
          return false
        } else {
          return true
        }
      },
    },
  },
}
</script>

<style scoped>
.base-progress {
  height: 26px;
  width: 400px;
  border-radius: 15px;
  background-color: #272425;
  border: 3px solid #272425;
  box-sizing: border-box;
  margin-bottom: 30px;
}
.inner {
  position: relative;
  background: #379bff;
  border-radius: 15px;
  height: 25px;
  box-sizing: border-box;
  left: -3px;
  top: -2px;
}
.inner span {
  position: absolute;
  right: 0;
  top: 26px;
}
</style>

2、根组件App.vue

<template>
  <div class="app">
    <BaseProgress :w="width"></BaseProgress>
  </div>
</template>

<script>
import BaseProgress from './components/BaseProgress.vue'
export default {
  data() {
    return {
      width: 30,
    }
  },
  components: {
    BaseProgress,
  },
}
</script>
<style>
</style>

prop & data、单向数据流

　　

 1、components/BaseCount.vue

<template>
  <div class="base-count">
    <button @click="handleSub">-</button>
    <span>{{ count }}</span>
    <button @click="handleAdd">+</button>
  </div>
</template>

<script>
export default {
  // 1.自己的数据随便修改  （谁的数据 谁负责）
  // data () {
  //   return {
  //     count: 100,
  //   }
  // },
  // 2.外部传过来的数据 不能随便修改
  props: {
    count: {
      type: Number,
    },
  },
  methods: {
    handleSub() {
      // 通知父组件数据变化
      this.$emit('changeCount', this.count - 1)
    },
    handleAdd() {
      this.$emit('changeCount', this.count + 1)
    },
  },
}
</script>

<style>
.base-count {
  margin: 20px;
}
</style>

2、根组件App.vue

<template>
  <div class="app">
    <BaseCount :count="count" @changeCount="handleChange"></BaseCount>
  </div>
</template>

<script>
import BaseCount from './components/BaseCount.vue'
export default {
  components:{
    BaseCount
  },
  data(){
    return {
      count:100
    }
  },
  methods:{
    handleChange(newVal){
      // console.log(newVal);
      this.count = newVal
    }
  }
}
</script>
<style>
</style>

 

子组件修改父组件的值的三种方式

　　如果父组件传给子组件的数据，子组件想修改，有以下三种方式：
　　1、子传父，在子组件通知父组件修改
　　2、在子组件通过this.$parent.父组件中的属性 = xxxx
　　3、通过在父组件中传值的时候，属性名加上.sync，放权给子组件修改props中的数据，然后通过this.emit('update:props传过来的属性名'， 要修改成什么值)

　　

 

组件通信案例：小黑记事本-组件版

1、组件目录下

components/TodoFooter.vue

<template>
  <!-- 统计和清空 -->
  <footer class="footer">
    <!-- 统计 -->
    <span class="todo-count"
      >合 计:<strong> {{ list.length }} </strong></span
    >
    <!-- 清空 -->
    <button class="clear-completed" @click="clear">清空任务</button>
  </footer>
</template>

<script>
export default {
  props: {
    list: {
      type: Array,
    },
  },
  methods:{
    clear(){
      this.$emit('clear')
    }
  }
}
</script>

<style>
</style>

components/TodoHeader.vue

<template>
   <!-- 输入框 -->
  <header class="header">
    <h1>小黑记事本</h1>
    <input placeholder="请输入任务" class="new-todo" v-model="todoName" @keyup.enter="handleAdd"/>
    <button class="add" @click="handleAdd">添加任务</button>
  </header>
</template>

<script>
export default {
  data(){
    return {
      todoName:''
    }
  },
  methods:{
    handleAdd(){
      // console.log(this.todoName)
      this.$emit('add',this.todoName)
      this.todoName = ''
    }
  }
}
</script>

<style>

</style>

components/TodoMain.vue

<template>
  <!-- 列表区域 -->
  <section class="main">
    <ul class="todo-list">
      <li class="todo" v-for="(item, index) in list" :key="item.id">
        <div class="view">
          <span class="index">{{ index + 1 }}.</span>
          <label>{{ item.name }}</label>
          <button class="destroy" @click="handleDel(item.id)"></button>
        </div>
      </li>
    </ul>
  </section>
</template>

<script>
export default {
  props: {
    list: {
      type: Array,
    },
  },
  methods: {
    handleDel(id) {
      this.$emit('del', id)
    },
  },
}
</script>

<style>
</style>

2、样式style/index.css

html,
body {
  margin: 0;
  padding: 0;
}
body {
  background: #fff;
}
button {
  margin: 0;
  padding: 0;
  border: 0;
  background: none;
  font-size: 100%;
  vertical-align: baseline;
  font-family: inherit;
  font-weight: inherit;
  color: inherit;
  -webkit-appearance: none;
  appearance: none;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font: 14px 'Helvetica Neue', Helvetica, Arial, sans-serif;
  line-height: 1.4em;
  background: #f5f5f5;
  color: #4d4d4d;
  min-width: 230px;
  max-width: 550px;
  margin: 0 auto;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-weight: 300;
}

:focus {
  outline: 0;
}

.hidden {
  display: none;
}

#app {
  background: #fff;
  margin: 180px 0 40px 0;
  padding: 15px;
  position: relative;
  box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.2), 0 25px 50px 0 rgba(0, 0, 0, 0.1);
}
#app .header input {
  border: 2px solid rgba(175, 47, 47, 0.8);
  border-radius: 10px;
}
#app .add {
  position: absolute;
  right: 15px;
  top: 15px;
  height: 68px;
  width: 140px;
  text-align: center;
  background-color: rgba(175, 47, 47, 0.8);
  color: #fff;
  cursor: pointer;
  font-size: 18px;
  border-radius: 0 10px 10px 0;
}

#app input::-webkit-input-placeholder {
  font-style: italic;
  font-weight: 300;
  color: #e6e6e6;
}

#app input::-moz-placeholder {
  font-style: italic;
  font-weight: 300;
  color: #e6e6e6;
}

#app input::input-placeholder {
  font-style: italic;
  font-weight: 300;
  color: gray;
}

#app h1 {
  position: absolute;
  top: -120px;
  width: 100%;
  left: 50%;
  transform: translateX(-50%);
  font-size: 60px;
  font-weight: 100;
  text-align: center;
  color: rgba(175, 47, 47, 0.8);
  -webkit-text-rendering: optimizeLegibility;
  -moz-text-rendering: optimizeLegibility;
  text-rendering: optimizeLegibility;
}

.new-todo,
.edit {
  position: relative;
  margin: 0;
  width: 100%;
  font-size: 24px;
  font-family: inherit;
  font-weight: inherit;
  line-height: 1.4em;
  border: 0;
  color: inherit;
  padding: 6px;
  box-shadow: inset 0 -1px 5px 0 rgba(0, 0, 0, 0.2);
  box-sizing: border-box;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.new-todo {
  padding: 16px;
  border: none;
  background: rgba(0, 0, 0, 0.003);
  box-shadow: inset 0 -2px 1px rgba(0, 0, 0, 0.03);
}

.main {
  position: relative;
  z-index: 2;
}

.todo-list {
  margin: 0;
  padding: 0;
  list-style: none;
  overflow: hidden;
}

.todo-list li {
  position: relative;
  font-size: 24px;
  height: 60px;
  box-sizing: border-box;
  border-bottom: 1px solid #e6e6e6;
}

.todo-list li:last-child {
  border-bottom: none;
}

.todo-list .view .index {
  position: absolute;
  color: gray;
  left: 10px;
  top: 20px;
  font-size: 22px;
}

.todo-list li .toggle {
  text-align: center;
  width: 40px;
  /* auto, since non-WebKit browsers doesn't support input styling */
  height: auto;
  position: absolute;
  top: 0;
  bottom: 0;
  margin: auto 0;
  border: none; /* Mobile Safari */
  -webkit-appearance: none;
  appearance: none;
}

.todo-list li .toggle {
  opacity: 0;
}

.todo-list li .toggle + label {
  /*
        Firefox requires `#` to be escaped - https://bugzilla.mozilla.org/show_bug.cgi?id=922433
        IE and Edge requires *everything* to be escaped to render, so we do that instead of just the `#` - https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/7157459/
    */
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23ededed%22%20stroke-width%3D%223%22/%3E%3C/svg%3E');
  background-repeat: no-repeat;
  background-position: center left;
}

.todo-list li .toggle:checked + label {
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23bddad5%22%20stroke-width%3D%223%22/%3E%3Cpath%20fill%3D%22%235dc2af%22%20d%3D%22M72%2025L42%2071%2027%2056l-4%204%2020%2020%2034-52z%22/%3E%3C/svg%3E');
}

.todo-list li label {
  word-break: break-all;
  padding: 15px 15px 15px 60px;
  display: block;
  line-height: 1.2;
  transition: color 0.4s;
}

.todo-list li.completed label {
  color: #d9d9d9;
  text-decoration: line-through;
}

.todo-list li .destroy {
  display: none;
  position: absolute;
  top: 0;
  right: 10px;
  bottom: 0;
  width: 40px;
  height: 40px;
  margin: auto 0;
  font-size: 30px;
  color: #cc9a9a;
  margin-bottom: 11px;
  transition: color 0.2s ease-out;
}

.todo-list li .destroy:hover {
  color: #af5b5e;
}

.todo-list li .destroy:after {
  content: '×';
}

.todo-list li:hover .destroy {
  display: block;
}

.todo-list li .edit {
  display: none;
}

.todo-list li.editing:last-child {
  margin-bottom: -1px;
}

.footer {
  color: #777;
  padding: 10px 15px;
  height: 20px;
  text-align: center;
  border-top: 1px solid #e6e6e6;
}

.footer:before {
  content: '';
  position: absolute;
  right: 0;
  bottom: 0;
  left: 0;
  height: 50px;
  overflow: hidden;
  box-shadow: 0 1px 1px rgba(0, 0, 0, 0.2), 0 8px 0 -3px #f6f6f6,
    0 9px 1px -3px rgba(0, 0, 0, 0.2), 0 16px 0 -6px #f6f6f6,
    0 17px 2px -6px rgba(0, 0, 0, 0.2);
}

.todo-count {
  float: left;
  text-align: left;
}

.todo-count strong {
  font-weight: 300;
}

.filters {
  margin: 0;
  padding: 0;
  list-style: none;
  position: absolute;
  right: 0;
  left: 0;
}

.filters li {
  display: inline;
}

.filters li a {
  color: inherit;
  margin: 3px;
  padding: 3px 7px;
  text-decoration: none;
  border: 1px solid transparent;
  border-radius: 3px;
}

.filters li a:hover {
  border-color: rgba(175, 47, 47, 0.1);
}

.filters li a.selected {
  border-color: rgba(175, 47, 47, 0.2);
}

.clear-completed,
html .clear-completed:active {
  float: right;
  position: relative;
  line-height: 20px;
  text-decoration: none;
  cursor: pointer;
}

.clear-completed:hover {
  text-decoration: underline;
}

.info {
  margin: 50px auto 0;
  color: #bfbfbf;
  font-size: 15px;
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.5);
  text-align: center;
}

.info p {
  line-height: 1;
}

.info a {
  color: inherit;
  text-decoration: none;
  font-weight: 400;
}

.info a:hover {
  text-decoration: underline;
}

/*
    Hack to remove background from Mobile Safari.
    Can't use it globally since it destroys checkboxes in Firefox
*/
@media screen and (-webkit-min-device-pixel-ratio: 0) {
  .toggle-all,
  .todo-list li .toggle {
    background: none;
  }

  .todo-list li .toggle {
    height: 40px;
  }
}

@media (max-width: 430px) {
  .footer {
    height: 50px;
  }

  .filters {
    bottom: 10px;
  }
}

3、根组件App.vue

<template>
  <!-- 主体区域 -->
  <section id="app">
    <TodoHeader @add="handleAdd"></TodoHeader>
    <TodoMain :list="list" @del="handelDel"></TodoMain>
    <TodoFooter :list="list" @clear="clear"></TodoFooter>
  </section>
</template>

<script>
import TodoHeader from './components/TodoHeader.vue'
import TodoMain from './components/TodoMain.vue'
import TodoFooter from './components/TodoFooter.vue'

// 渲染功能：
// 1.提供数据： 提供在公共的父组件 App.vue
// 2.通过父传子，将数据传递给TodoMain
// 3.利用 v-for渲染

// 添加功能：
// 1.手机表单数据  v-model
// 2.监听事件（回车+点击都要添加）
// 3.子传父，讲任务名称传递给父组件 App.vue
// 4.进行添加 unshift（自己的数据自己负责）
// 5.清空文本框输入的内容
// 6.对输入的空数据 进行判断

// 删除功能
// 1.监听事件（监听删除的点击） 携带id
// 2.子传父，讲删除的id传递给父组件的App.vue
// 3.进行删除filter（自己的数据 自己负责）

// 底部合计：父传子  传list 渲染
// 清空功能：子传父  通知父组件 → 父组件进行更新
// 持久化存储：watch深度监视list的变化 -> 往本地存储 ->进入页面优先读取本地数据
export default {
  data() {
    return {
      list: JSON.parse(localStorage.getItem('list')) || [
        { id: 1, name: '打篮球' },
        { id: 2, name: '看电影' },
        { id: 3, name: '逛街' },
      ],
    }
  },
  components: {
    TodoHeader,
    TodoMain,
    TodoFooter,
  },
  watch: {
    list: {
      deep: true,
      handler(newVal) {
        localStorage.setItem('list', JSON.stringify(newVal))
      },
    },
  },
  methods: {
    handleAdd(todoName) {
      // console.log(todoName)
      this.list.unshift({
        id: +new Date(),
        name: todoName,
      })
    },
    handelDel(id) {
      // console.log(id);
      this.list = this.list.filter((item) => item.id !== id)
    },
    clear() {
      this.list = []
    },
  },
}
</script>

<style>
</style>

4、main.js 需要引入css

import Vue from 'vue'
import App from './App.vue'
import './style/index.css'

Vue.config.productionTip = false

new Vue({
  render: h => h(App),
}).$mount('#app')

 

非父子通信(拓展) -event bus 事件总线

　　

 1、utils/EventBus.js

import Vue from 'vue'

// 定义事件总线
const Bus  =  new Vue()
// 导出
export default Bus

2、组件目录下

components/BaseA.vue

<template>
  <div class="base-a">
    我是A组件（接受方）
    <p>{{msg}}</p>  
  </div>
</template>

<script>
import Bus from '../utils/EventBus'
export default {
  data() {
    return {
      msg: '',
    }
  },
  created() {
    Bus.$on('sendMsg', (msg) => {
      // console.log(msg)
      this.msg = msg
    })
  },
}
</script>

<style scoped>
.base-a {
  width: 200px;
  height: 200px;
  border: 3px solid #000;
  border-radius: 3px;
  margin: 10px;
}
</style>

components/BaseB.vue

<template>
  <div class="base-b">
    <div>我是B组件（发布方）</div>
    <button @click="sendMsgFn">发送消息</button>
  </div>
</template>

<script>
import Bus from '../utils/EventBus'
export default {
  methods: {
    sendMsgFn() {
      Bus.$emit('sendMsg', '今天天气不错，适合旅游')  // 触发事件
    },
  },
}
</script>

<style scoped>
.base-b {
  width: 200px;
  height: 200px;
  border: 3px solid #000;
  border-radius: 3px;
  margin: 10px;
}
</style>

components/BaseC.vue

<template>
  <div class="base-c">
    我是C组件（接受方）
    <p>{{msg}}</p>  
  </div>
</template>

<script>
import Bus from '../utils/EventBus'
export default {
  data() {
    return {
      msg: '',
    }
  },
  created() {
    Bus.$on('sendMsg', (msg) => {  // 监听事件
      // console.log(msg)
      this.msg = msg
    })
  },
}
</script>

<style scoped>
.base-c {
  width: 200px;
  height: 200px;
  border: 3px solid #000;
  border-radius: 3px;
  margin: 10px;
}
</style>

3、根组件App.vue

<template>
  <div class="app">
    <BaseA></BaseA>
    <BaseB></BaseB>
    <BaseC></BaseC>
  </div>
</template>

<script>
import BaseA from './components/BaseA.vue'
import BaseB from './components/BaseB.vue'
import BaseC from './components/BaseC.vue'
export default {
  components:{
    BaseA,
    BaseB,
    BaseC
  }
}
</script>
<style>
</style>

 

非父子通信(拓展) -provide & inject

　　

1、组件目录下

components/GrandSon.vue

<template>
  <div class="grandSon">
    我是GrandSon
    {{ color }} -{{ userInfo.name }} -{{ userInfo.age }}
  </div>
</template>

<script>
export default {
  inject: ['color', 'userInfo'],
}
</script>

<style>
.grandSon {
  border: 3px solid #000;
  border-radius: 6px;
  margin: 10px;
  height: 100px;
}
</style>

components/SonA.vue

<template>
  <div class="SonA">我是SonA组件
    <GrandSon></GrandSon>
  </div>
</template>

<script>
import GrandSon from '../components/GrandSon.vue'
export default {
  components:{
    GrandSon
  }
}
</script>

<style>
.SonA {
  border: 3px solid #000;
  border-radius: 6px;
  margin: 10px;
  height: 200px;
}
</style>

components/SonB.vue

<template>
  <div class="SonB">
    我是SonB组件
  </div>
</template>

<script>
export default {

}
</script>

<style>
.SonB {
  border: 3px solid #000;
  border-radius: 6px;
  margin: 10px;
  height: 200px;
}
</style>

2、根组件App.vue

<template>
  <div class="app">
    我是APP组件
    <button @click="change">修改数据</button>
    <SonA></SonA>
    <SonB></SonB>
  </div>
</template>

<script>
import SonA from './components/SonA.vue'
import SonB from './components/SonB.vue'
export default {
  provide() {
    return {
      // 简单类型 是非响应式的
      color: this.color,
      // 复杂类型 是响应式的
      userInfo: this.userInfo,
    }
  },
  data() {
    return {
      color: 'pink',
      userInfo: {
        name: 'zs',
        age: 18,
      },
    }
  },
  methods: {
    change() {
      this.color = 'red'
      this.userInfo.name = 'ls'
    },
  },
  components: {
    SonA,
    SonB,
  },
}
</script>

<style>
.app {
  border: 3px solid #000;
  border-radius: 6px;
  margin: 10px;
}
</style>

进阶语法

v-model 原理

　　

 

1、组件目录下 

components/MyInput.vue

<template>
  <input
    type="text"
    :value="value"
    @input="$emit('input', $event.target.value)"
  />
</template>

<script>
export default {
  name: 'MyInput',
  props: ['value']
}
</script>
<style lang="less" scoped></style>

components/MySelect.vue

<template>
  <select :value="value" @change="$emit('input', $event.target.value)">
    <option value="北京">北京市</option>
    <option value="上海">上海市</option>
    <option value="广州">广州市</option>
    <option value="深圳">深圳市</option>
  </select>
</template>

<script>
export default {
  name: 'MySelect',
  props: ['value']
}
</script>
<style lang="less" scoped></style>

2、根组件App.vue

<template>
  <div>
    <h3>需求1：不用v-model实现双向绑定</h3>
    <input type="text" :value="uname" @input="changeValue" />   <!-- 等同于 ->   <input type="text" v-model="uname"> -->
    <p>结论：v-model 可以拆分成 :value + @input</p>
    <hr />

    <h3>需求2：实现输入框组件的v-model</h3>
    <!-- <MyInput v-model="age"></MyInput> -->
    <!-- <MyInput :value="age" @input="changeAge"></MyInput> -->
    <MyInput v-model="age"></MyInput>
    <p>结论：组件的v-model需要子组件的配合。</p>
    <p>结论：子组件需要接收value属性，并触发input事件</p>
    <hr />

    <h3>需求3：实现下拉框组件的v-model</h3>
    <MySelect v-model="address"></MySelect>
    <!-- <MySelect :value="address" @input="changeSelect"></MySelect> -->
    <p>下拉框的v-model相当于 :value + @input</p>

    <hr />
    <p>总结：v-model ==== :value + @input</p>
    <p>总结：父传子，为了把数据传给子组件，设置表单元素的默认值</p>
    <p>总结：子传父，为了把表单元素的值，传给父组件，修改data数据</p>
  </div>
</template>

<script>
import MyInput from './components/MyInput.vue'
import MySelect from './components/MySelect.vue'
export default {
  data () {
    return {
      address: '上海',
      age: 20,
      uname: 'zhangsan'
    }
  },
  components: {
    MyInput,
    MySelect
  },
  methods: {
    changeValue (e) {
      // 把输入框的值，赋值给uname
      this.uname = e.target.value
    },
    changeAge (val) {
      this.age = val
    },
    changeSelect (val) {
      this.address = val
    }
  }
}
</script>

<style lang="less" scoped>
p {
  background-color: gold;
}
</style>

.sync 修饰符

　　

1、组件目录下

components/MyDialog.vue

<template>
  <div class="dialog" v-show="abc">
    <div class="dialog-header">
      <h3>友情提示</h3>
      <span class="close" @click="$emit('update:abc', false)">✖️</span>
    </div>
    <div class="dialog-content">我是文本内容</div>
    <div class="dialog-footer">
      <button>取消</button>
      <button>确认</button>
    </div>
  </div>
</template>

<script>
export default {
  props: ['abc']
}
</script>

<style scoped>
* {
  margin: 0;
  padding: 0;
}

.dialog {
  width: 470px;
  height: 230px;
  padding: 0 25px;
  background-color: #ffffff;
  margin: 40px;
  border-radius: 5px;
}

.dialog-header {
  height: 70px;
  line-height: 70px;
  font-size: 20px;
  border-bottom: 1px solid #ccc;
  position: relative;
}

.dialog-header .close {
  position: absolute;
  right: 0px;
  top: 0px;
  cursor: pointer;
}

.dialog-content {
  height: 80px;
  font-size: 18px;
  padding: 15px 0;
}

.dialog-footer {
  display: flex;
  justify-content: flex-end;
}

.dialog-footer button {
  width: 65px;
  height: 35px;
  background-color: #ffffff;
  border: 1px solid #e1e3e9;
  cursor: pointer;
  outline: none;
  margin-left: 10px;
  border-radius: 3px;
}

.dialog-footer button:last-child {
  background-color: #007acc;
  color: #fff;
}
</style>

2、根组件App.vue

<template>
  <div>
    <button @click="abc = true">删除</button>

    <!-- 等同于  =>  <MyDialog :abc="abc" @update:abc="handle"></MyDialog> -->
    <!-- :abc="abc" 表示向子组件传值 -->
    <!-- @update:abc="handle" 表示监听子组件的通知, 子组件通知必须是 update:abc 这个函数名,  update:固定的   abc为自定义属性名, 随便改啥都行，保持一致即可 -->

    <!-- abc 是自定义的属性名 -->
    <MyDialog :abc.sync="abc"></MyDialog>

    <!-- 
      :属性.sync="变量"
       等同于 :属性="变量"  +  @update:属性="xxx"
    -->
  </div>
</template>

<script>
import MyDialog from './components/MyDialog.vue'
export default {
  data() {
    return {
      abc: false // 控制弹层显示和隐藏
    }
  },
  // methods: {
  //   handle(val) {
  //     this.abc = val
  //   },
  // },
  components: {
    MyDialog
  }
}
</script>

<style>
body {
  background-color: #b3b3b3;
}
</style>

ref 和 $refs

　　

　　

1、组件目录下

components/MyForm.vue

<template>
  <div>
    <h3>Form组件需求：点击按钮能够重置表单</h3>
    用户名：<input type="text" v-model="uname" /><br />
    手机号：<input type="text" v-model="phone" /><br />
  </div>
</template>

<script>
export default {
  data () {
    return {
      uname: 'zhangsan',
      phone: '13266668888'
    }
  },
  methods: {
    // 清空方法
    resetForm () {
      this.uname = this.phone = ''
    }
  }
}
</script>

<style lang="less" scoped></style>

components/MyTest.vue

<template>
  <div>
    <h3>Test组件需求：找到下面的p标签，设置样式</h3>
    <p ref="abc">这是Test组件中的p标签</p>
  </div>
</template>

<script>
export default {
  mounted () {
    // document.querySelector 是在整个页面中找元素
    // document.querySelector('p').style.color = 'red'
    // 通过$refs获取dom
    // this.$refs.abc 就和document.querySelector('p')一个意思，获取到ref值为abc的组件，这样就可以调用组件中的方法
    this.$refs.abc.style.color = 'blue'
    // 1. 如果组件中，多个元素有相同的ref值， this.$refs.xxx 只找最后一个
    // 2. 循环出来之后，多个元素有相同的ref值， this.$refs.xxx 找到全部
  }
}
</script>
<style lang="less" scoped></style>

2、根组件App.vue

<template>
  <div>
    <h2>App组件</h2>
    <p ref="abc">这是App组件中的p标签</p>
    <hr />
    <MyTest></MyTest>
    <hr />
    <MyForm ref="myform"></MyForm>
    // 通过$refs获取组件
    <!-- $refs.myform 找到ref值为myform的组件, 就可以调用组件中的方法 -->
    <button @click="$refs.myform.resetForm()">重置</button>
  </div>
</template>

<script>
import MyTest from './components/MyTest.vue'
import MyForm from './components/MyForm.vue'
export default {
  data () {
    return {}
  },
  components: {
    MyTest,
    MyForm
  }
}
</script>
<style lang="less" scoped></style>

自定义指令focus、loading

1、在main.js中定义

import Vue from 'vue'
import App from './App.vue'

Vue.config.productionTip = false

// 1. 全局注册指令
Vue.directive('focus', {
  // 进入页面，让元素自动获取焦点
  inserted (ele) {
    // console.log(ele)     // 绑定指令的元素
    // console.log(binding) // 指令的一些信息（比如包括指令的值  binding.value）
    ele.focus() // 让元素获取焦点
  }
})

new Vue({
  render: h => h(App)
}).$mount('#app')

2、自定义指令的使用，在根组件中App.vue

<template>
  <!-- <div class="box" @click="$event.target.innerHTML = 'HELLO'"> -->
  <div class="box">

    <!-- 使用自定义指令 color -->
    <h3 v-color="yanse">需求1：让输入框立即获取焦点</h3>

    <div class="focus">
      <!-- 使用全局的自定义指令  v-focus -->
      <input type="text" v-focus />
    </div>

    <h3>需求2：Ajax请求数据，并设计loading指令</h3>
    <!-- list数据为空，加 loading 类，让loading图片显示 -->
    <!-- list数据不为空，移除 loading 类，让loading图片隐藏 -->
    <!-- 使用局部定义的指令  loading -->
    <ul v-loading="list.length">
      <li class="news" v-for="item in list" :key="item.id">
        <div class="left">
          <div class="title">{{ item.title }}</div>
          <div class="info">
            <span>{{ item.source }}</span>
            <span>{{ item.time }}</span>
          </div>
        </div>
        <div class="right">
          <img :src="item.img" alt="" />
        </div>
      </li>
    </ul>
  </div>
</template>

<script>
// 安装 axios =>  npm i axios 或者 yarn add axios
// 安装如果报错，则加 --legacy-peer-deps 选项
// 接口地址：http://hmajax.itheima.net/api/news
// 请求方式：get
// 请求参数：无

import axios from 'axios'
export default {
  directives: {
    loading: {
      // 刷新页面后，立即判断有没有数据，loading图片要不要显示
      inserted(ele, obj) {
        // console.log(ele) // 使用指令的元素
        // console.log(obj.value) // 指令的值
        obj.value <= 0
          ? ele.classList.add('loading')
          : ele.classList.remove('loading')
      },
      update(ele, obj) {
        obj.value <= 0
          ? ele.classList.add('loading')
          : ele.classList.remove('loading')
      }
    },
    color: {
      inserted(ele, obj) {
        console.log('111111111')
        // console.log(ele) // element 元素，表示使用指令的那个元素
        // console.log(obj) // obj.value 就是传递给指令的值
        ele.style.color = obj.value
      },
      update(ele, obj) {
        console.log(22222222222222)
        ele.style.color = obj.value
      }
    },
  },
  data() {
    return {
      yanse: 'blue',
      list: []
    }
  },
  async created() {
    const { data: res } = await axios.get('http://hmajax.itheima.net/api/news')
    setTimeout(() => {
      this.list = res.data
    }, 2000)
  },
  methods: {
    // showEle(e) {
    //   console.log(e.target)
    // }
  }
}
</script>

<style>
.loading::before {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: #fff url('./loading.gif') no-repeat;
  content: '';
}

.box {
  width: 800px;
  min-height: 500px;
  position: relative;
}

.focus,
ul {
  border: 3px solid orange;
  border-radius: 5px;
  padding: 10px;
  margin: 10px;
}

.news {
  display: flex;
  height: 120px;
  width: 600px;
  margin: 0 auto;
  padding: 20px 0;
  cursor: pointer;
}

.news .left {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding-right: 10px;
}

.news .left .title {
  font-size: 20px;
}

.news .left .info {
  color: #999999;
}

.news .left .info span {
  margin-right: 20px;
}

.news .right {
  width: 160px;
  height: 120px;
}

.news .right img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
</style>

Vue异步更新、$nextTick

　　使用场景：
　　　　如果想在修改数据后立刻得到更新后的DOM结构，可以使用this.$nextTick()
　　　　在created生命周期中进行DOM操作

　　

 

　　

 

<template>
  <div>
    <!-- 需求：输入框和确认按钮默认隐藏；点击编辑显示；显示后立即获取焦点 -->
    <div class="title">
      <h2>大标题</h2>
      <button @click="showIpt">编辑</button>
    </div>
    <div class="form" v-show="flag">
      <input type="text" ref="refIpt" />
      <button>确认</button>
    </div>
  </div>
</template>

<script>
export default {
  data () {
    return {
      flag: false
    }
  },
  methods: {
    showIpt () {
      this.flag = true // 修改flag，让输入框显示
      // this.flag = false
      // this.flag = true
      // this.flag = false
      // this.flag = true
      // 上述，数据更新了，页面不会立即更新；会在下次循环的时候更新页面。

      this.$nextTick(() => {
        // 数据更新后，页面也更新后。这个函数执行
        this.$refs.refIpt.focus() // 找到输入框，让其获得焦点
      })
    }
  }
}
</script>

<style lang="less" scoped>
.title {
  width: 300px;
  display: flex;
  justify-content: flex-start;
  align-items: center;
  button {
    margin-left: 5px;
  }
}
</style>