Can ref get an instance of vue? Several ways to access instances

In Vue, component instances are created by Vue instances. In a component, we can use ref to get a reference to a DOM element or component instance. So, can I use ref to get a Vue instance?

The short answer is no. Because a Vue instance is not a DOM element or component, but a JavaScript object. Although the Vue instance will eventually be rendered as a DOM element on the page, using ref in the component can only obtain a reference to the DOM element or component instance, and cannot directly obtain the Vue instance.

Then the question is, what should I do if I need to access the Vue instance? Here are several common methods:

1. Use Vue.mixin global mixin

We can use Vue.mixin global mixin to mix an object into all Vue components . In the mixin object, we can define a created (or other life cycle hook function), and then the Vue instance can be accessed through this. The sample code is as follows:

// mixin.js 
export default { 
  created() { 
    console.log('Vue instance:', this.$root); 
  } 
} 
// main.js 
import Vue from 'vue'; 
import App from './App.vue'; 
import mixin from './mixin'; 

Vue.mixin(mixin); 

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

A created hook function is defined in mixin.js to output a Vue instance when the component is created. In main.js we apply the mixin globally.

2. Use $root to access the Vue instance

As mentioned earlier, the Vue instance can be accessed through this.$root. In the component, we can also get the Vue instance through this.$root. When using this.$root in a component to access a Vue instance, you need to pay attention. You must use it after the Vue instance is created, otherwise undefined will be returned. The sample code is as follows:

<template> 
  <div> 
    <p>Using $root to access Vue instance:</p> 
    <button @click="logVueInstance">Log Vue Instance</button> 
  </div> 
</template> 

<script> 
  export default { 
    methods: { 
      logVueInstance() { 
        console.log('Vue instance:', this.$root); 
      } 
    } 
  } 
</script>

defines a method in the component to output a Vue instance when the button is clicked.

3. Use $parent to access the Vue instance

In addition to using $root, we can also access the Vue instance of the parent component through $parent. If the parent component is the root component, then It's the entire Vue instance. It is also important to note that the parent component must have been created before using $parent access. The sample code is as follows:

<template> 
  <div> 
    <p>Using $parent to access Vue instance:</p> 
    <button @click="logVueInstance">Log Vue Instance</button> 
  </div> 
</template> 

<script> 
  export default { 
    methods: { 
      logVueInstance() { 
        console.log('Vue instance:', this.$parent.$root); 
      } 
    } 
  } 
</script>

defines a method in the component. When the button is clicked, the Vue instance of the parent component is accessed through $parent and output.

To summarize, although the Vue instance cannot be accessed directly through ref, we can use Vue.mixin, $root, $parent and other methods to access the Vue instance in the component.

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