Vuetify rendering v-datatable automatically - vue.js

Question

I have a problem v-datatable rendering each time I change a v-select.
I´d like it render only when I click in a button, I created to do fetch data from server.
Here is the codepen: https://codepen.io/luizalves/pen/VwrwXwE?editors=101
For now, it´s rendering all times I change the v-select.
data:()=>({
grupos: [
{ id: 1, nome: 'Diário', ffi: 'YYYY-MM-DD', fff: 'DD-MM-YYYY' },
{ id: 2, nome: 'Mensal', ffi: 'YYYY-MM', fff: 'MM-YYYY' },
{ id: 3, nome: 'Anual', ffi: 'YYYY', fff: 'YYYY' },
],
grupo:1
headers: [
{ text: 'Data', value: 'label', sortable: false },
{ text: 'Total(R$) ', value: 'total', sortable: false },
],
)}
// data-table
<v-select
v-model="grupo"
label="Grupado por"
:items="grupos"
item-text="nome"
item-value="id"
class="purple-input"
/>
<v-btn
class="mt-1 mr-3"
color="info"
#click.stop="getEstatisticasPeriodo()"
>
Pesquisar
</v-btn>
<v-data-table
:headers="headers"
:items="result_dados"
:items-per-page="3"
:footer-props="{
'items-per-page-options': [3, 5, 10, 20, 30, 40, 50],
}"
class="elevation-1"
>
<template
v-for="(header, i) in headers"
#[`item.${header.value}`]="{ item }"
>
<template v-if="header.value !== 'actions'">
<span :key="i">
{{ formatColumn(item, header) }}
</span>
</template>
</template>
</v-data-table>
methods: {
formatColumn(item, col) {
if (!item[col.value]) return ''
if (['total'].includes(col.value)) {
const formatado = Number(item[col.value]).toLocaleString('pt-BR', {
style: 'currency',
currency: 'BRL',
})
return formatado
}
if (['label'].includes(col.value)) {
const ffi = this.grupos.find((m) => m.id == this.grupo).ffi
const fff = this.grupos.find((m) => m.id == this.grupo).fff
return this.$moment(item[col.value], ffi).format(fff)
} else return item[col.value]
},
getEstatisticasPeriodo(){
// fetch api data
}
....

Answer 1

Any data value you access in formatCalories will be added the list of watched values. When the value changes, it will re-render the view and call formatCalories. To solve that issue, I just created a selectValue property that is only set when the button is clicked.
new Vue({
el: '#app',
vuetify: new Vuetify(),
data () {
return {
group: 1,
selectValue: 1,
groups: [
{ id: 1, name: 'day'},
{ id: 2, name: 'month' },
{ id: 3, name: 'year' },
],
headers: [
{
text: 'Dessert (100g serving)',
align: 'start',
sortable: false,
value: 'name',
},
{ text: 'Calories', value: 'calories' },
{ text: 'Fat (g)', value: 'fat' },
{ text: 'Carbs (g)', value: 'carbs' },
{ text: 'Protein (g)', value: 'protein' },
{ text: 'Iron (%)', value: 'iron' },
],
desserts: [
{
name: 'Frozen Yogurt',
calories: 159,
fat: 6.0,
carbs: 24,
protein: 4.0,
iron: '1%',
},
{
name: 'Ice cream sandwich',
calories: 237,
fat: 9.0,
carbs: 37,
protein: 4.3,
iron: '1%',
},
{
name: 'Eclair',
calories: 262,
fat: 16.0,
carbs: 23,
protein: 6.0,
iron: '7%',
},
{
name: 'Cupcake',
calories: 305,
fat: 3.7,
carbs: 67,
protein: 4.3,
iron: '8%',
},
{
name: 'Gingerbread',
calories: 356,
fat: 16.0,
carbs: 49,
protein: 3.9,
iron: '16%',
},
{
name: 'Jelly bean',
calories: 375,
fat: 0.0,
carbs: 94,
protein: 0.0,
iron: '0%',
},
{
name: 'Lollipop',
calories: 392,
fat: 0.2,
carbs: 98,
protein: 0,
iron: '2%',
},
{
name: 'Honeycomb',
calories: 408,
fat: 3.2,
carbs: 87,
protein: 6.5,
iron: '45%',
},
{
name: 'Donut',
calories: 452,
fat: 25.0,
carbs: 51,
protein: 4.9,
iron: '22%',
},
{
name: 'KitKat',
calories: 518,
fat: 26.0,
carbs: 65,
protein: 7,
iron: '6%',
},
],
}
},
methods: {
onSubmit() {
this.selectValue = this.$refs.select.value;
},
formatCalories(calories) {
const suffix = {
1: '-red',
2: '-orange',
3: '-green'
};
return calories + suffix[this.selectValue];
}
},
})
<div id="app">
<v-app id="inspire">
<v-row>
<v-col cols='3'>
<v-btn elevation="2" #click="onSubmit"> Submit </v-btn>
<v-select
v-model="group"
label="Grouped by"
:items="groups"
item-text="name"
item-value="id"
class="purple-input"
ref="select"
/>
</v-col>
</v-row>
<v-data-table
:headers="headers"
:items="desserts"
class="elevation-1"
>
<template v-slot:item.calories="{ item }">
{{ formatCalories(item.calories) }}
</template>
</v-data-table>
</v-app>
</div>