Why using $refs in interpolation fails and leads to errors in Vue.js 2.x components

Question

Why using $refs in interpolation fails and leads to errors in Vue.js 2.x components

Here is a codepen I created: codepen

const sidebar = {
  name: "sidebar",
  template: "<p>SIDEBAR</p>",
  data() {
    return {
      active: true
    };
  },
  methods: {
    test() {
      alert("test: " + this.active)
    }
  }
};
new Vue({
  el: '#app',
  name: 'vue-instance',
  
  data() {
    return {
      title: "Title of the page"
    };
  }, 
  components: {
    sidebar: sidebar,  
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
    {{ title }}
  
    <sidebar ref="sidebar1">
    </sidebar>
  
  <button type="button" v-on:click="$refs.sidebar1.test()">Test sidebar</button>
   
<!-- {{ $refs.sidebar1.active }} this causes error! -->
  {{ $refs }}
</div>

The issue arises from the commented line:

"message": "$refs.sidebar1 is undefined",

This means that during rendering, the parent component's $refs collection is empty. However, upon clicking the button, $refs can access sidebar1 correctly.

Why does this occur? Is there a way to make {{ $refs.sidebar1.active }} work in the parent component template?

Thank you for your help!

javascript vue.js vuejs2

Answer 1

Answer №1

What is the reason behind this? How can one achieve the interpolation of $refs.sidebar1.active in the parent component template?

In Vue, refs are populated only when child components are created within the parent's render function, and the refs field is not reactive. When a click handler is specified, it is wrapped in a function that executes only upon clicking the button, at which point the refs have already been set (as the initial rendering process is complete) and there is no error.

For more information, refer to the Vue documentation: Accessing Child Component Instances

A possible solution for the given example would be to use props to control the child component from outside and utilize the sync modifier to allow the child to change the prop similar to using v-model. It is advisable to extract the work with refs into a parent function as well:

const sidebar = {
  name: "sidebar",
  template: "<p>SIDEBAR</p>",
  props: ['active'],
  methods: {
    test() {
      alert("test: " + this.active)
    }
  }
};
new Vue({
  el: '#app',
  name: 'vue-instance',
  
  data() {
    return {
      active: false,
      title: "Title of the page"
    };
  }, 
  methods: {
    testChild() {
      this.$refs.sidebar1.test();
    }
  },
  components: {
    sidebar: sidebar,  
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
    {{ title }}
  
    <sidebar ref="sidebar1" :active.sync="active">
    </sidebar>
  
  <button type="button" v-on:click="active = !active">Toggle</button>
  <button type="button" v-on:click="testChild">Test child</button>
   
<!--      {{ $refs.sidebar1.active }} this causes error! -->
  {{ active }}
</div>

Answer 2

What is the reason behind this? How can one achieve the interpolation of $refs.sidebar1.active in the parent component template?

In Vue, refs are populated only when child components are created within the parent's render function, and the refs field is not reactive. When a click handler is specified, it is wrapped in a function that executes only upon clicking the button, at which point the refs have already been set (as the initial rendering process is complete) and there is no error.

For more information, refer to the Vue documentation: Accessing Child Component Instances

A possible solution for the given example would be to use props to control the child component from outside and utilize the sync modifier to allow the child to change the prop similar to using v-model. It is advisable to extract the work with refs into a parent function as well:

const sidebar = {
  name: "sidebar",
  template: "<p>SIDEBAR</p>",
  props: ['active'],
  methods: {
    test() {
      alert("test: " + this.active)
    }
  }
};
new Vue({
  el: '#app',
  name: 'vue-instance',
  
  data() {
    return {
      active: false,
      title: "Title of the page"
    };
  }, 
  methods: {
    testChild() {
      this.$refs.sidebar1.test();
    }
  },
  components: {
    sidebar: sidebar,  
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
    {{ title }}
  
    <sidebar ref="sidebar1" :active.sync="active">
    </sidebar>
  
  <button type="button" v-on:click="active = !active">Toggle</button>
  <button type="button" v-on:click="testChild">Test child</button>
   
<!--      {{ $refs.sidebar1.active }} this causes error! -->
  {{ active }}
</div>

Why using $refs in interpolation fails and leads to errors in Vue.js 2.x components

Answer №1

Similar questions

Using VueJS to assign data within a method function

What are the steps to transforming a regular expression into a dynamic format?

Unlocking the contents of an array from a separate file in Next.js

A guide on organizing dates in a datatable using the dd-MMM-yyyy hh:mm tt format

Ways to ensure that the dropdown content remains visible even after the mouse has exited the trigger element

Vue in d3 - the property ownerDocument is not defined

JavaScript can be used to create a fullscreen experience without any toolbars, scrollbars, and the like, without having

javascript strange behavior

Mismatched units px and rem (existing fixes are ineffective)

Fulfill a promise based on a particular event in Puppeteer

Show PDF within the browser using ajax technology

Using the HTML form element to achieve two-way binding on array elements

Toggle the ASP validation control using JavaScript

Short-circuiting async flows on non-error events in Node.js

Steps for eliminating an element using jQuery from a variable filled with HTML code

Having trouble with the Jquery Slider script?

What is the best way to halt the ticking of this clock in JavaScript?

Our system has picked up on the fact that your website is failing to verify reCAPTCHA solutions using Google reCAPTCHA V2

Managing Asynchronous Operations in Vuex

React components multiplying with every click, tripling or even quadrupling in number