Vue - access nested childs using ref

Question

I have vue component which I use inside himself - data can have array with subelements and I use this array to render them in loop, and next level, next level etc. according to nesting level.

Now I would like to run child method from parent and then - if statements are ok, also call it to child, next level etc.

I use

    <mycomponent
            ref="myFirstLevelRefName"
            (...)
    ></mycomponent>

and then:

this.$refs.myFirstLevelRefName 

to call first-level childs. But what about about child nodes? I use them in view in that way:

    <mycomponent
            v-for="(subElement, index) in getSubelements()"
            ref="???"
            v-bind:data="subElement"
            v-bind:key="index"
    ></mycomponent>

I tried sent this.$refs from child level to console, but it's empty.

How should I set ref name in nested elements and then call them from parent?

Answer 1

While it is technically possible to access $refs of nested children...

Vue.component('mycomponent', {
    template: "#mycomponent",
});

new Vue({
  el: '#app',
  mounted() {
    console.log(
      'Second level <input>\'s value:',
      this.$refs.myFirstLevelRefName.$refs.mySecondLevelRefName.value
    )
  }
})

<script src="https://unpkg.com/vue/dist/vue.min.js"></script>

<template id="mycomponent">
    <div>
        <input ref="mySecondLevelRefName" value="Hello">
    </div>
</template>

<div id="app">
  <mycomponent ref="myFirstLevelRefName"></mycomponent>
</div>

A way of performing parent/deep child, or deep ancestor/sibling communication, for simple scenarios, is using an event hub. (For complex scenarios, see Vuex.)

You would create a global variable:

var eventHub = new Vue(); // use a Vue instance as event hub

To emit events you would use in any component:

eventHub.$emit('myevent', 'some value');

You would, then, in any other component, to listen to that event. The action of that event could be anything, including a method call (which is what you want):

eventHub.$on('myevent', (e) => {
    console.log('myevent received', e)
    // this.callSomeMethod();
});

Demo:

var eventHub = new Vue(); // use a Vue instance as event hub

Vue.component('component-first', {
    template: "#component-1st",
    methods: {
      myMethod() {
        eventHub.$emit('myevent', 'some value');
      }
    }
});
Vue.component('component-second', {template: "#component-2nd"});
Vue.component('component-third', {
  template: "#component-3rd",
  created() {
    eventHub.$on('myevent', (e) => {
      this.check();
    });
  },
  methods: {
    check() {
      console.log('check method called at 3rd level child');
    }
  }
})

new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue.js!'
  }
})

<script src="https://unpkg.com/vue/dist/vue.min.js"></script>

<template id="component-1st">
    <div>
        1st level component
        <button @click="myMethod">Trigger event at 1st level component that will call 3rd level child's method</button>
        <hr>
        <component-second></component-second>
    </div>
</template>
<template id="component-2nd">
    <div>
        <component-third></component-third>
    </div>
</template>
<template id="component-3rd">
    <div><h1>3rd level child</h1></div>
</template>

<div id="app">
  <component-first></component-first>
</div>

Note: If creating a dedicated instance as event hub is something complicated in your environment, you can replace eventHub with this.$root (inside your components) and use your own Vue instance as hub.