Vue動態組件

前面的話

　　讓多個組件使用同一個掛載點，並動態切換，這就是動態組件。本文將詳細介紹Vue動態組件

 

概述

　　經過使用保留的 <component> 元素，動態地綁定到它的 is 特性，能夠實現動態組件

<div id="example">
  <button @click="change">切換頁面</button>
  <component :is="currentView"></component>
</div>

<script>
var home = {template:'<div>我是主頁</div>'};
var post = {template:'<div>我是提交頁</div>'};
var archive = {template:'<div>我是存檔頁</div>'};
new Vue({
  el: '#example',
  components: {
    home,
    post,
    archive,
  },
  data:{
    index:0,
    arr:['home','post','archive'],
  },
  computed:{
    currentView(){
        return this.arr[this.index];
    }
  },
  methods:{
    change(){
      this.index = (++this.index)%3;
    }
  }
})
</script>

　　也能夠直接綁定到組件對象上

<div id="example">
  <button @click="change">切換頁面</button>
  <component :is="currentView"></component>
</div>

<script>
new Vue({
  el: '#example',
  data:{
    index:0,
    arr:[
      {template:`<div>我是主頁</div>`},
      {template:`<div>我是提交頁</div>`},
      {template:`<div>我是存檔頁</div>`}
    ],
  },
  computed:{
    currentView(){
        return this.arr[this.index];
    }
  },
  methods:{
    change(){
      this.index = (++this.index)%3;
    }
  }
})
</script>

 

緩存

　　<keep-alive> 包裹動態組件時，會緩存不活動的組件實例，而不是銷燬它們。和 <transition> 類似，<keep-alive> 是一個抽象組件：它自身不會渲染一個 DOM 元素，也不會出如今父組件鏈中

【基礎用法】

<div id="example">
  <button @click="change">切換頁面</button>
  <keep-alive>
    <component :is="currentView"></component>  
  </keep-alive>
</div>

<script>
new Vue({
  el: '#example',
  data:{
    index:0,
    arr:[
      {template:`<div>我是主頁</div>`},
      {template:`<div>我是提交頁</div>`},
      {template:`<div>我是存檔頁</div>`}
    ],
  },
  computed:{
    currentView(){
        return this.arr[this.index];
    }
  },
  methods:{
    change(){
      let len = this.arr.length;
      this.index = (++this.index)% len;
    }
  }
})
</script>

【條件判斷】

　　若是有多個條件性的子元素，<keep-alive> 要求同時只有一個子元素被渲染

<div id="example">
  <button @click="change">切換頁面</button>
  <keep-alive>
    <home v-if="index===0"></home>
    <posts v-else-if="index===1"></posts>
    <archive v-else></archive>  
  </keep-alive>
</div>

<script>
new Vue({
  el: '#example',
  components:{
    home:{template:`<div>我是主頁</div>`},
    posts:{template:`<div>我是提交頁</div>`},
    archive:{template:`<div>我是存檔頁</div>`},
  },
  data:{
    index:0,
  },
  methods:{
    change(){
      let len = Object.keys(this.$options.components).length;
      this.index = (++this.index)%len;
    }
  }
})
</script>

【activated 和 deactivated】 

　　activated 和 deactivated 在 <keep-alive> 樹內的全部嵌套組件中觸發

<div id="example">
  <button @click="change">切換頁面</button>
  <keep-alive>
    <component :is="currentView" @pass-data="getData"></component> 
  </keep-alive>
  <p>{{msg}}</p>
</div>

<script>
new Vue({
  el: '#example',
  data:{
    index:0,
    msg:'',    
    arr:[
      { 
        template:`<div>我是主頁</div>`,
        activated(){
          this.$emit('pass-data','主頁被添加');
        },
        deactivated(){
          this.$emit('pass-data','主頁被移除');
        },        
      },
      {template:`<div>我是提交頁</div>`},
      {template:`<div>我是存檔頁</div>`}
    ],
  },
  computed:{
    currentView(){
        return this.arr[this.index];
    }
  },
  methods:{
    change(){
      var len = this.arr.length;
      this.index = (++this.index)% len;
    },
    getData(value){
      this.msg = value;
      setTimeout(()=>{
        this.msg = '';
      },500)
    }
  }
})
</script>

【include和exclude】

　　include 和 exclude 屬性容許組件有條件地緩存。兩者均可以用逗號分隔字符串、正則表達式或一個數組來表示

<!-- 逗號分隔字符串 -->
<keep-alive include="a,b">
  <component :is="view"></component>
</keep-alive>
<!-- 正則表達式 (使用 v-bind) -->
<keep-alive :include="/a|b/">
  <component :is="view"></component>
</keep-alive>
<!-- Array (use v-bind) -->
<keep-alive :include="['a', 'b']">
  <component :is="view"></component>
</keep-alive>

　　匹配首先檢查組件自身的 name 選項，若是 name 選項不可用，則匹配它的局部註冊名稱（父組件 components 選項的鍵值）。匿名組件不能被匹配

  <keep-alive include="home,archive">
    <component :is="currentView"></component> 
  </keep-alive>

　　上面的代碼，表示只緩存home和archive，不緩存posts

<div id="example">
  <button @click="change">切換頁面</button>
  <keep-alive include="home,archive">
    <component :is="currentView"></component> 
  </keep-alive>
</div>
<script src="https://unpkg.com/vue"></script>
<script>
new Vue({
  el: '#example',
  data:{
    index:0,   
    arr:[
      {name:'home',template:`<div>我是主頁</div>`},
      {name:'posts',template:`<div>我是提交頁</div>`},
      {name:'archive',template:`<div>我是存檔頁</div>`}
    ],
  },
  computed:{
    currentView(){
        return this.arr[this.index];
    }
  },
  methods:{
    change(){
      var len = this.arr.length;
      this.index = (++this.index)% len;
    },
  }
})
</script>