vue.js - Vuetify issue with v-menu

Question

Vuetify 1.1.8 / Vue 2.5.16

I don't understand why I get 2 different behaviors :

1- testing in Codepen.io

html

    <div id="app">
      <v-app id="inspire">
        <div class="text-xs-center">
          <v-menu offset-y>
            <v-btn
              slot="activator"
              color="primary"
              dark
            >
              <span v-if="this.locale === 'en'">English</span>
              <span v-if="this.locale === 'fr'">Fran?ais</span>
              <span v-if="this.locale === 'br'">Português</span>
            </v-btn>
            <v-list>
              <v-list-tile
                v-for="(locale, index) in locales"
                :key="index"
                @click="switchLocale(index)"
              >
                <v-list-tile-title>{{ locale.title }}</v-list-tile-title>
              </v-list-tile>
            </v-list>
          </v-menu>
        </div>
      </v-app>
    </div>

js

    new Vue({
      el: '#app',
      data: () => ({
        locale: 'en',
        locales: [
          { locale: 'en', title: 'English', icon: '@/assets/images/flag_gb_24.png' },
          { locale: 'fr', title: 'Fran?ais', icon: '@/assets/images/flag_fr_24.png' },
          { locale: 'br', title: 'Português', icon: '@/assets/images/flag_br_24.png' }
        ]
      }),
       methods: {
        switchLocale: function (index) {
          console.log('switch locale: ', this.locales[index].title)
          this.locale = this.locales[index].locale
        }
      }
    })

is running fine...

BUT once I insert it into a Vue.js component in my app, I get an error :

console

    vuetify.js?ce5b:19387 [Vuetify] Unable to locate target [data-app]

    found in

    ---> <VMenu>
           <VToolbar>
             <Toolbar>
               <App> at src/App.vue
                 <Root>
    consoleWarn @ vuetify.js?ce5b:19387
    initDetach @ vuetify.js?ce5b:16782
    mounted @ vuetify.js?ce5b:16742
    callHook @ vue.runtime.esm.js?2b0e:2917
    insert @ vue.runtime.esm.js?2b0e:4154
    invokeInsertHook @ vue.runtime.esm.js?2b0e:5956
    patch @ vue.runtime.esm.js?2b0e:6175
    Vue._update @ vue.runtime.esm.js?2b0e:2666
    updateComponent @ vue.runtime.esm.js?2b0e:2784
    get @ vue.runtime.esm.js?2b0e:3138
    run @ vue.runtime.esm.js?2b0e:3215
    flushSchedulerQueue @ vue.runtime.esm.js?2b0e:2977
    (anonymous) @ vue.runtime.esm.js?2b0e:1833
    flushCallbacks @ vue.runtime.esm.js?2b0e:1754
    Promise.then (async)
    microTimerFunc @ vue.runtime.esm.js?2b0e:1802
    nextTick @ vue.runtime.esm.js?2b0e:1846
    queueWatcher @ vue.runtime.esm.js?2b0e:3064
    update @ vue.runtime.esm.js?2b0e:3205
    Vue.$forceUpdate @ vue.runtime.esm.js?2b0e:2687
    (anonymous) @ index.js?6435:233
    (anonymous) @ index.js?6435:231
    (anonymous) @ index.js?6435:116
    (anonymous) @ Toolbar.vue?be73:29
    ./src/components/Shared/Toolbar.vue @ app.js:2759
    __webpack_require__ @ app.js:768
    hotApply @ app.js:687
    (anonymous) @ app.js:344
    Promise.then (async)
    hotUpdateDownloaded @ app.js:343
    hotAddUpdateChunk @ app.js:319
    webpackHotUpdateCallback @ app.js:37
    (anonymous) @ app.a888e56db407050b2768.hot-update.js:1
    Toolbar.vue?9799:67 TOOLBAR mounted locale:  en

Toolbar.vue

       <template>
          <v-toolbar height="80px" fixed>
            <v-toolbar-title>
              <img src="@/assets/images/app_logo.png" alt="">
              <v-menu offset-y>
                <v-btn
                  slot="activator"
                  color="primary"
                  dark
                >
                  <span v-if="this.locale === 'en'">English</span>
                  <span v-if="this.locale === 'fr'">Fran?ais</span>
                  <span v-if="this.locale === 'br'">Português</span>
                </v-btn>
                <v-list>
                  <v-list-tile
                    v-for="(locale, index) in locales"
                    :key="index"
                    @click="switchLocale(index)"
                  >
                    <v-list-tile-title>{{ locale.title }}</v-list-tile-title>
                  </v-list-tile>
                </v-list>
              </v-menu>
            </v-toolbar-title>
            <v-spacer></v-spacer>
            <v-toolbar-items>
              ....
            </v-toolbar-items>
       </v-toolbar>
    </template>

    <script>
    export default {
      name: 'Toolbar',
      props: ['appName'],
      data () {
        return {
          menuItems: {
            home: { icon: 'home', title: 'Home', link: '/' },
            about: { icon: 'info', title: 'About', link: '/about' }
          },
          locale: 'en',
          locales: [
            { locale: 'en', title: 'English', icon: '@/assets/images/flag_gb_24.png' },
            { locale: 'fr', title: 'Fran?ais', icon: '@/assets/images/flag_fr_24.png' },
            { locale: 'br', title: 'Português', icon: '@/assets/images/flag_br_24.png' }
          ]
        }
      },
      methods: {
        switchLocale: function (index) {
          console.log('switch locale: ', this.locales[index].title)
          this.locale = this.locales[index].locale
        }
      },
      mounted () {
        console.log('TOOLBAR mounted locale: ', this.locale)
      }
    }
    </script>

Answer 1

As far as I understand, in vuetify you need to wrap your application in <v-app></v-app>. This happens in App.vue or whatever you have set in your main.js as root component. The v-app components sets this data-app attribute.

The documentation says this about it:

Vuetify requires the use of the v-app component. It should wrap your entire application and is the center point for much of the framework functionality including themes. Ensure that you are following the proper markup documented in the Application page.

Source: FAQ: My application does not look correct, retrieved on 2 October 2019