What problem does vue slot solve?

The problem solved by the vue slot: Content is not allowed to be written in the middle of the introduced sub-component tags. Slot is a capability provided by Vue for component packagers; it allows developers to define uncertain parts that are expected to be specified by the user as slots when packaging components; slots can be considered as during component packaging. A placeholder for content reserved for the user.

The operating environment of this tutorial: windows7 system, vue3 version, DELL G3 computer.

What is a slot?

We know that in vue, content is not allowed to be written in the middle of the introduced sub-component tags. In order to solve this problem, the official introduced the concept of slot.

Slots are actually equivalent to placeholders. It gives your HTML template a place in the component, allowing you to pass in some stuff. Slots are divided into anonymous slots, named slots and scoped slots.

You may not quite understand why I need to pass HTML into the subcomponent instead of writing it directly in the subcomponent? The answer is this. You can imagine a scenario where you have five pages. Only one area of ​​the five pages has different content. How would you write these five pages? Copy and paste is one way, but in vue, slots are better.

##Anonymous slot

---

Anonymous slot, we can call it a single slot slot or default slot. In contrast to named slots, it does not require the name attribute to be set. (Its hidden name attribute is default.)

Example:

The file directory is as follows, and the Home component is the parent component of HelloWorld.

Write an anonymous slot in HelloWorld

<template>
  <div>
     Helloworld组件

     <div>
       <slot></slot>
     </div>

  </div>
</template>

<script>
export default {

}
</script>

<!-- Add "scoped" attribute to limit CSS to this component only -->
<style>
.hello{
  width:100%;
  height:300px;
  background:#ccc;
  margin-top:50px;
  .slotTxt{
    width:500px;
    height:200px;
    margin:30px auto;
    background:red;
  }
}
</style>

Introduce sub-component in Home component and add it in sub-component Content written in the component tag

<template>
  <div>
    我是Home父组件
    <helloworld>
      <!-- 没有插槽，这里的内容不显示 -->
      <h1>我是helloworld中的插槽啊</h1>  
    </helloworld>
  </div>
</template>

<script>
import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
export default {
  name: &#39;home&#39;,
  components: {
    HelloWorld
  }
}
</script>

Effect

It is not difficult to see that the content (red part) in the HelloWorld tag has been displayed.

Named Slot

---

As mentioned above, the slot has a name attribute. As opposed to anonymous slots, anonymous slots with the name attribute added are named slots.

Write the slots whose name attributes are left and right respectively in the HelloWorld component

<template>
  <div>
     Helloworld组件

     <div>
       <slot></slot>
     </div>

     <div>
       <slot></slot>
     </div>

  </div>
</template>

<script>
export default {

}
</script>

<!-- Add "scoped" attribute to limit CSS to this component only -->
<style>
.hello{
  width:700px;
  height:300px;
  background:#ccc;
  margin: 0 auto;
  margin-top:50px;
  .slotLeft{
    width:300px;
    height:200px;
    float:left;
    background:red;
  }
  .slotRight{
    width:300px;
    height:200px;
    float:right;
    background:pink;
  }
}
</style>

Home component writes v-slot:name on the template Use named slots

<template>
  <div>
    我是Home父组件
    <helloworld>
      <template>
         <h1>name属性为left</h1> 
      </template>
      <template>
         <h1>name属性为right</h1> 
      </template>
     
    </helloworld>
  </div>
</template>

<script>
import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
export default {
  name: &#39;home&#39;,
  components: {
    HelloWorld
  }
}
</script>
<style>
.home{
  width:900px;
  margin:0 auto;
  background:yellow;
  padding-bottom:100px;
}
</style>

Note that v-slot can only be added on the template tag (with one exception).

• Effect

##Exception (Abandoned slot='name ')

Named slots with slot attributes have been abandoned since 2.6.0, and vue3.x has been completely abandoned. Only cli before vue3 can be used.
• 
  

  <template>
    <div>
      我是Home父组件
      <helloworld>
        <h1>name属性为left</h1>  
        <h1>name属性为right</h1>  
      </helloworld>
    </div>
  </template>
  
  <script>
  import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
  export default {
    name: &#39;home&#39;,
    components: {
      HelloWorld
    }
  }
  </script>
  <style>
  .home{
    width:900px;
    margin:0 auto;
    background:yellow;
    padding-bottom:100px;
  }
  </style>

The effect is the same as above.

Little knowledge about named slots

Like v-on and v-bind, v-slot also has an abbreviation, that is, replace everything before the parameter (v-slot:) with character#. For example v-slot:header can be rewritten as #header.
• 
  

Scope slot

A scope slot is actually a slot that can pass data. If some data in the child component is to be used in the parent component, it must be passed through specified methods. A rule is proposed in the official documentation that **all content in the parent template is compiled in the parent scope. Everything inside a child template is compiled in the child scope. **If you use the value in the child component directly in the parent component, an error will be reported.

---

Scope slot of anonymous slot

In order to make the data in the child component available in the parent's slot content, we can use the data as the element's A property is bound:

语法：v-bind:users="user"

Subcomponent HelloWorld code

• <template>
    <div>
       Helloworld组件  
       <div>
         <slot></slot>
       </div> 
       
    </div>
  </template>
  
  <script>
  export default {
    data(){
      return{
        user:{
          name:&#39;oralinge&#39;,
          age:18
        }
      }  
    }
  }
  </script>
  
  <!-- Add "scoped" attribute to limit CSS to this component only -->
  <style>
  .hello{
    width:700px;
    height:300px;
    background:#ccc;
    margin: 0 auto;
    margin-top:50px;
    .slotLeft{
      width:300px;
      height:200px;
      // float:left;
      background:red;
      margin:20px auto
    }
    .slotRight{
      width:300px;
      height:200px;
      float:right;
      background:pink;
    }
  }
  </style>

The property bound to the element (v-bind:users="user") is called for the slot prop. Now in the parent scope, we can use v-slot with a value to define the name of the slot prop we provide.

语法：v-slot:default="随意取的名字"  // default可省略，简写为v-slot="随意取的名字"

Parent component Home code

• <template>
    <div>
      我是Home父组件
      <helloworld>
        <template>
           <h1>{{slotProps.users.name}}</h1> 
        </template>
      </helloworld>
    </div>
  </template>
  
  <script>
  import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
  export default {
    name: &#39;home&#39;,
    components: {
      HelloWorld
    }
  }
  </script>
  <style>
  .home{
    width:900px;
    margin:0 auto;
    background:yellow;
    padding-bottom:100px;
  }
  </style>

Note:

The slotProps in the parent component can be taken at will.

The users in the sub-component are chosen at will, corresponding to the users in the parent component.
The user in the subcomponent is data.

Effect

The scope slot of the named slot

The same as the anonymous slot, only You need to replace default with the name value of the slot.

Sub component HelloWorld code

• <template>
    <div>
       Helloworld组件  
       <div>
         <slot></slot>
       </div> 
       
    </div>
  </template>
  
  <script>
  export default {
    data(){
      return{
        user:{
          name:&#39;hello world&#39;,
          age:18
        }
      }  
    }
  }
  </script>
  
  <!-- Add "scoped" attribute to limit CSS to this component only -->
  <style>
  .hello{
    width:700px;
    height:300px;
    background:#ccc;
    margin: 0 auto;
    margin-top:50px;
    .slotLeft{
      width:300px;
      height:200px;
      // float:left;
      background:red;
      margin:20px auto
    }
    .slotRight{
      width:300px;
      height:200px;
      float:right;
      background:pink;
    }
  }
  </style>

Parent component Home code

• <template>
    <div>
      我是Home父组件
      <helloworld>
        <template>
           <h1>{{slotProps.users.name}}</h1> 
        </template>
      </helloworld>
    </div>
  </template>
  
  <script>
  import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
  export default {
    name: &#39;home&#39;,
    components: {
      HelloWorld
    }
  }
  </script>
  <style>
  .home{
    width:900px;
    margin:0 auto;
    background:yellow;
    padding-bottom:100px;
  }
  </style>

Effect

注意：
     默认插槽的缩写语法不能和具名插槽混用，因为它会导致作用域不明确。

另，slot-scope写法在2.6之后已废弃，作用与上面相同，在此不做解释。

上面的写法是不是觉得有些麻烦？别着急，我们来看一看解构插槽 Prop。

解构插槽 Prop

作用域插槽的内部工作原理是将你的插槽内容包括在一个传入单个参数的函数里：

function (slotProps) {
  // 插槽内容
}

这意味着 v-slot 的值实际上可以是任何能够作为函数定义中的参数的 JavaScript 表达式。所以在支持的环境下 (单文件组件或现代浏览器)，你也可以使用 ES2015 解构来传入具体的插槽 prop。

语法：v-slot="{ users }"

• HelloWold组件

<template>
  <div>
     Helloworld组件  
     <div>
       <slot></slot>
     </div> 
     
  </div>
</template>

<script>
export default {
  data(){
    return{
      user:{
        name:&#39;hello world&#39;,
        age:18
      }
    }  
  }
}
</script>

<!-- Add "scoped" attribute to limit CSS to this component only -->
<style>
.hello{
  width:700px;
  height:300px;
  background:#ccc;
  margin: 0 auto;
  margin-top:50px;
  .slotLeft{
    width:300px;
    height:200px;
    // float:left;
    background:red;
    margin:20px auto
  }
  .slotRight{
    width:300px;
    height:200px;
    float:right;
    background:pink;
  }
}
</style>

• Home组件

<template>
  <div>
    我是Home父组件
    <helloworld>
      <template>
         <h1>{{users.name}}</h1> 
      </template>
    </helloworld>
  </div>
</template>

<script>
import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
export default {
  name: &#39;home&#39;,
  components: {
    HelloWorld
  }
}
</script>
<style>
.home{
  width:900px;
  margin:0 auto;
  background:yellow;
  padding-bottom:100px;
}
</style>

• 效果
  

• 重命名----更改users这个名字

<template>
  <div>
    我是Home父组件
    <helloworld>
      <template>
         <h1>{{person.name}}</h1> 
      </template>
    </helloworld>
  </div>
</template>

<script>
import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
export default {
  name: &#39;home&#39;,
  components: {
    HelloWorld
  }
}
</script>
<style>
.home{
  width:900px;
  margin:0 auto;
  background:yellow;
  padding-bottom:100px;
}
</style>

效果如上图。

• 定义后备内容，用于插槽 prop 是 undefined 的情形
  此处按照官方文档的写法会出现语法报错，后期应该会修复（有知道的麻烦通知一声）。

<template>
  <div>
    我是Home父组件
    <helloworld>
      <template>
         <h1>{{users.name}}</h1> 
      </template>
    </helloworld>
  </div>
</template>

<script>
import HelloWorld from &#39;@/components/HelloWorld.vue&#39;
export default {
  name: &#39;home&#39;,
  components: {
    HelloWorld
  }
}
</script>
<style>
.home{
  width:900px;
  margin:0 auto;
  background:yellow;
  padding-bottom:100px;
}
</style>

使用场景

---

• 复用公共组件
  代码示例如下：

<template>
  <div>
    <div>
      <span>{{title}}</span>
      <div>
        <slot></slot>
      </div>
    </div>
    <div>
      <slot></slot>
    </div>
  </div>
</template>
<script>
export default {
  data () {
    return {
    }
  },
  props: {
    title: {
      type: String,
      required: true
    }
  }
}
</script>
<style>
.title-box {
  padding: 16px 0;
  border-bottom: 1px solid #eff1f5;
  .title {
    font-family: MicrosoftYaHei;
    font-size: 24px;
    color: #283039;
    letter-spacing: 0;
    line-height: 24px;
    &::before {
      width: 4px;
      margin-right: 20px;
      content: "";
      background-color: #5da1ff;
      display: inline-block;
      height: 20px;
      vertical-align: middle;
    }
  }
  .right {
    float: right;
    margin-right: 20px;
  }
}
</style>

使用的ui框架为ivew。

相关推荐：vue.js视频教程

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