Components defined in the vue component cannot be accessed

In Vue development, we usually use components to encapsulate some reusable functions. Sometimes we may encounter a situation where components defined within the component are inaccessible, which often causes us some trouble. This article will explain in detail why the components defined in the Vue component are inaccessible and how to solve this problem.

1. Reason

The data, methods, life cycle hooks, etc. of the Vue component are all encapsulated within the scope of the component, and the same is true for the components defined inside the component. Therefore, components defined inside a component cannot be directly accessed outside the component.

For example, in the following example, we define a parent component and a child component, and introduce the child component in the parent component:

// 父组件
<template>
  <div>
    <child-component></child-component>
  </div>
</template>

<script>
import ChildComponent from './ChildComponent.vue'; // 引入子组件

export default {
  name: 'ParentComponent',
  components: {
    ChildComponent // 注册子组件
  }
}
</script>

// 子组件
<template>
  <h1>这是子组件</h1>
</template>

<script>
export default {
  name: 'ChildComponent',
}
</script>

However, if we directly outside the child component Access the subcomponent, for example:

console.log(ChildComponent);

At this time, undefined will be output, indicating that the subcomponent cannot be accessed. This is because child components can only be recognized and accessed within the scope of the parent component, and child components are not exposed to the global scope.

2. Solution

So, how to make the components defined in the parent component accessible outside the component? The following are two possible methods:

2.1. Using $refs

In Vue components, each component has a unique identifier $refs, which can be used to access the component or DOM element. Therefore, we can get the child component through $refs in the parent component to access the components inside the child component.

Modify the above example code, add a button to the parent component, and access the subcomponent through $refs in the button's click event:

// 父组件
<template>
  <div>
    <child-component></child-component>
    <button @click="accessChildComponent">访问子组件</button>
  </div>
</template>

<script>
import ChildComponent from './ChildComponent.vue'; // 引入子组件

export default {
  name: 'ParentComponent',
  components: {
    ChildComponent // 注册子组件
  },
  methods: {
    accessChildComponent() {
      console.log(this.$refs.childComponent.$children) // 访问子组件内部组件
    }
  }
}
</script>

// 子组件
<template>
  <div ref="childComponent">
    <h1>这是子组件</h1>
  </div>
</template>

<script>
export default {
  name: 'ChildComponent',
  components: {
    SubComponent: {
      name: 'SubComponent',
      template: '<div>这是子组件内部组件</div>'
    }
  }
}
</script>

In the above code, we add Add a ref attribute so that it is mounted to the $refs attribute of the parent component. Then, in the click event of the parent component, we access the child component object through $refs.childComponent, and obtain the components inside the child component object through the $children property.

2.2. Using mixins

In addition to $refs, Vue also provides a concept of mixins (mixing in). Mixins can provide some common logic or code snippets for components, thereby improving code reusability. Therefore, we can expose the components inside the child component to the parent component through mixins.

Modify the above example code, define a mixins in the subcomponent, and expose the components inside the subcomponent to the global scope in the mixins:

// 父组件
<template>
  <div>
    <button @click="accessChildComponent">访问子组件</button>
  </div>
</template>

<script>
import ChildComponent from './ChildComponent.vue'; // 引入子组件

export default {
  name: 'ParentComponent',
  components: {
    ChildComponent // 注册子组件
  },
  methods: {
    accessChildComponent() {
      console.log(window.$SubComponent) // 访问子组件内部组件
    }
  }
}
</script>

// 子组件
<template>
  <h1>这是子组件</h1>
</template>

<script>
const SubComponent = {
  name: 'SubComponent',
  template: '<div>这是子组件内部组件</div>'
}

export default {
  name: 'ChildComponent',
  mixins: [{
    created() {
      window.$SubComponent = SubComponent
    }
  }]
}
</script>

In the above code, we A mixins is defined in the component to expose the components inside the subcomponent to the global scope. Specifically, we define the SubComponent object as a constant and mount it to the $SubComponent property of the global scope in the created hook of mixins. Then, in the parent component, we can access the components inside the subcomponent through window.$SubComponent.

3. Summary

The above are two ways to solve the problem of inaccessible components defined in Vue components, which are to use $refs and mixins. $refs are suitable for directly accessing the components inside the child component in the parent component, while mixins are suitable for exposing the components inside the child component to the global scope. For specific needs, we can choose the appropriate solution based on the actual situation.

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