vue.js doesn't update on mounted() hook

Question

Edit : Solved, see answer.

So i'm new to vue.js and quasar so it is probably a rookie mistake about vue lifecycle hooks and vue reactivity.

I want to resize an element based on the browser's size. The height of this element is calculated using the height of other elements. I use $refs to get the other element's height and I capture the onResize() event launched by a quasar component.

This event is launched once when the page is loading, and my element's sizes are all 0 because I guess they are not rendered in the DOM yet. I have a method to refresh my calculated height, which I call when "onResize" event is captured, and also at the "mounted()" vue.js hook.

My problem is :

• the first onResize() calls the method but all elements have 0px in height.
• mounted() calls the method again and here all elements have their height calculated. The results are good, but it does not show on the display, see screenshot #1 : resize events and sizes logged in the console, note that the size is calculated twice, once on onResize() and once on mounted() . the one on mounted() has the good value but it does not show in the DOM.

• after I resize the window once, then everything is ok and i don't have any problem anymore. (screenshots #2 (window mode) and #3 (fullscreen again))

My question is : why the height is not update in the DOM when mounted() hook is called even if it is calculated correctly ? (everything is in the same .vue file)

My code : My problem is with the height of the div that has the "tableRow" ref

<template>
  <q-page>
    <div class="row" :style="'height: '+pageSize.height*0.95+'px;'">
      <div class="col-6 q-pa-lg">

        <div class="row" ref="actionsRow">
          <div class="col-6 q-mb-sm">
            <q-search hide-underline v-model="filter" />
          </div>
          <div class="col-6">

          </div>
        </div>

        <div class="row" ref="tableHeaderRow">
          <q-table class="col-12" :selection="selectionMode" :selected.sync="selectedRows" :data="templateTableData" :columns="templateColumns"
            row-key="slug" :pagination.sync="pagination" dense hide-bottom>
            <q-tr slot="body" slot-scope="props" :props="props">
            </q-tr>
          </q-table>
        </div>

        <div class="row" ref="tableRow" :style="'height: '+tableHeight+'px;'">
          <q-scroll-area style="height: 100%" class="col-12 q-mt-sm shadow-3">
            <q-table :selection="selectionMode" :selected.sync="selectedRows" :data="templateTableData" :columns="templateColumns" row-key="slug"
              :filter="filter" :pagination.sync="pagination" dense hide-bottom hide-header>
              <q-tr slot="body" slot-scope="props" :props="props" @click.native="onRowClick(props.row)" class="cursor-pointer">
                <q-td auto-width>
                  <q-checkbox color="primary" v-model="props.selected" />
                </q-td>
                <q-td v-for="col in props.cols" :key="col.name" :props="props">
                  {{ col.value }}
                </q-td>
              </q-tr>
            </q-table>
          </q-scroll-area>
        </div>

      </div>
      <router-view class="col-6 q-pa-lg">
      </router-view>
    </div>
    <q-window-resize-observable @resize="onResize" />
  </q-page>
</template>

Script:

var data = []
for (var i = 1; i <= 100; i++) {
  data.push({
    id: i,
    name: 'Template ' + i,
    slug: 'template' + i,
    active: true
  })
}

import { mapActions, mapGetters } from 'vuex'

export default {
  data: () => ({
    pageSize: {
      height: 0,
      width: 0
    },
    tableHeight: 0,
    templateColumns: [
      {
        name: 'templateName',
        required: true,
        label: 'Name',
        align: 'left',
        field: 'name',
        sortable: true
      },
      {
        name: 'templateSlug',
        label: 'Slug',
        align: 'left',
        field: 'slug',
        sortable: true
      },
      {
        name: 'templateActive',
        label: 'Active',
        align: 'left',
        field: 'active',
        sortable: true,
        sort: (a, b) => {
          if ((a && b) || (!a && !b)) {
            return 0
          } else if (a) {
            return 1
          } else {
            return -1
          }
        }
      }
    ],
    selectionMode: 'multiple',
    selectedRows: [],
    pagination: {
      sortBy: null, // String, column "name" property value
      descending: false,
      page: 1,
      rowsPerPage: 0 // current rows per page being displayed
    },
    templateTableData: data,
    filter: ''
  }),
  computed: {
    ...mapGetters('appUtils', [
      'getPageTitle',
      'allConst'
    ])
  },
  methods: {
    ...mapActions('appUtils', [
      'setPageTitle',
      'deletePageTitle'
    ]),
    onResize (size) {
      this.pageSize.height = size.height - this.getPageTitle.height
      this.resizeTable()
      console.log('ON RESIZE EVENT:')
      console.log('tableHeaderRow:'+
          this.$refs.tableHeaderRow.clientHeight)
      console.log('actionsRow:' + this.$refs.actionsRow.clientHeight)
      console.log('table:' + this.tableHeight)
    },
    onRowClick (row) {
      this.$router.push('/templates/' + row.slug)
    },
    resizeTable () {
      this.tableHeight = this.pageSize.height - this.$refs.actionsRow.clientHeight -
          this.$refs.tableHeaderRow.clientHeight - this.getPageTitle.height -
          this.allConst.templatePageHeaderMargins
    }
  },
  mounted () {
    console.log('MOUNT TEMPLATES')
    this.setPageTitle({ text: 'Manage templates', height: this.allConst.titleHeight })
    this.resizeTable()
    console.log('tableHeaderRow:' + this.$refs.tableHeaderRow.clientHeight)
    console.log('actionsRow:' + this.$refs.actionsRow.clientHeight)
    console.log('table:' + this.tableHeight)
  },
  destroyed () {
    console.log('DESTROY TEMPLATES')
    this.deletePageTitle()
  }
}

Answer 1

Another one of my variables (titleSize) was 0, like the other sizes, during the first onResize() event, and I did not take that into account to correct it during the mounted() Hook.