Vue/nuxt - how to access parents ref from child components

Question

I have a global confirm modal component that is registered on my default layout file, I would then try to access it from my pages/index.vue but the calling this.$refs there would just return an empty object. Placing the modal component in my pages/index.vue will work but it will defeat the purpose of my global confirm modal.

layouts/default.vue

<template lang="pug">
v-app(v-if="show")
  v-main
    transition
      nuxt
  confirm(ref='confirm')
</template>
<script>
import confirm from '~/components/confirm.vue'
export default {
  components: { confirm },
  data: () => ({
    show: false
  }),
  async created() {
    const isAuth = await this.$store.dispatch("checkAuth")
    if (!isAuth) return this.$router.push("/login")
    this.show = true
  }
}
</script>

components/confirm.vue

<template>
  <v-dialog v-model="dialog" :max-width="options.width" @keydown.esc="cancel">
    <v-card>
      <v-toolbar dark :color="options.color" dense flat>
        <v-toolbar-title class="white--text">{{ title }}</v-toolbar-title>
      </v-toolbar>
      <v-card-text v-show="!!message">{{ message }}</v-card-text>
      <v-card-actions class="pt-0">
        <v-spacer></v-spacer>
        <v-btn color="primary darken-1" @click.native="agree">Yes</v-btn>
        <v-btn color="grey" @click.native="cancel">Cancel</v-btn>
      </v-card-actions>
    </v-card>
  </v-dialog>
</template>
<script>
  export default {
    data: () => ({
      dialog: false,
      resolve: null,
      reject: null,
      message: null,
      title: null,
      options: {
        color: 'primary',
        width: 290
      }
    }),
    methods: {
      open(title, message, options) {
        this.dialog = true
        this.title = title
        this.message = message
        this.options = Object.assign(this.options, options)
        return new Promise((resolve, reject) => {
          this.resolve = resolve
          this.reject = reject
        })
      },
      agree() {
        this.resolve(true)
        this.dialog = false
      },
      cancel() {
        this.resolve(false)
        this.dialog = false
      }
    }
  }
</script>

I would then like to call it from my pages/index.vue like this (it would work if the ref is here but I would like a global confirm modal)

methods: {
    async openConfirm() {
      console.log("openConfirm")
       if (await this.$refs.confirm.open('Delete', 'Are you sure?', { color: 'red' })) {
         console.log('--yes')
       }else{
         console.log('--no')
       }
    },

Answer 1

The short answer is: Don't abuse $ref like that. Ultimately, it will just lead to anti-patterns wrapped in anti-patterns.

More detailed answer related to the exact task you're trying to accomplish: I've tackled this exact same thing (global, promise based confirmation dialogs) on a few Vue projects now, and this is what has worked really well so far:

1. Setup the confirm dialog as its own stand-alone 'module' so you can add it to main.js with two lines:

import ConfirmModule from './modules/confirm';
Vue.use(ConfirmModule);

(side point: there's a couple other of these 'global modular components' like alerts, etc...)

2. Use a JS file to orchestrate the setup process, the promise management, and the component instantiation. For example:

import vuetify from '@/plugins/vuetify';
import confirmDialog from './confirm-dialog.vue';

export default {
  install(Vue) {
    const $confirm = (title, text, options) => {
      const promise = new Promise((resolve, reject) => {
        try {
          let dlg = true;
          const props = {
            title, text, options, dlg,
          };
          const on = { };
          const comp = new Vue({
            vuetify,
            render: (h) => h(confirmDialog, { props, on }),
          });
          on.confirmed = (val) => {
            dlg = false;
            resolve(val);
            window.setTimeout(() => comp.$destroy(), 100);
          };

          comp.$mount();
          document.getElementById('app').appendChild(comp.$el);
        } catch (err) {
          reject(err);
        }
      });
      return promise;
    };

    Vue.prototype.$confirm = $confirm;
  },
};

3. Mount it to the Vue.prototype, this way you can use it from any component in your app simply by calling: this.$confirm(...)

4. When you build your Vue component (confirm-dialog.vue) you need only one-way bind your props for title, text and options, one-way bind the dlg prop to the dialog, or else setup a two-way binding through a computed property with a getter and setter... either way...

5. emit a "confirmed" event with true if the user confirms. So, from the confirm-dialog.vue component: this.$emit('confirmed', true);

6. If they dismiss the dialog, or click 'no' then emit false so that the promise doesn't hang around: this.$emit('confirmed', false);

7. Now, from any component, you can use it like so:

methods: {
  confirmTheThing() {
    this.$confirm('Do the thing', 'Are you really sure?', { color: 'red' })
      .then(confirmed => {
        if (confirmed) {
          console.log('Well OK then!');
        } else {
          console.log('Eh, maybe next time...');
        }
      });
  }
}

Answer 2

In nuxt project's default layout, put the component, say Confirm like below:

    <v-main>
      <v-container fluid>
        <nuxt />
        <Confirm ref="confirm" />
      </v-container>
    </v-main>

Then the component's open method can be used as below:

const confirmed = await this.$root.$children[2].$refs.confirm.open(...)
if (!confirmed) {
  return // user cancelled, stop here
}
// user confirmed, proceed

Tricky thing was how to find the component contained in the layout. $root.$children[2] part seemed working in development phase but once deployed, it had to be $root.$children[1] .

So I ended up doing below:

  // assume default.vue has data called 'COPYRIGHT_TEXT'
  const child = this.$root.$children.find(x => x.COPYRIGHT_TEXT)
  if (child) {
    const confirm = child.$refs.confirm
    if (confirm) {
      return await confirm.open(...)
    }
  }
  return false

Background: my project is in production but came up with a new requirement to get confirmation before any save in particular mode. I could use one-way event bus , but to do that, the rest of codes after confirmation would have to be refactored to be passed as a callback in every saving place.