Apply condition class to v-col - vue.js

Question

I'm trying to apply condition class to my v-col
<v-row v-for="(rule, index) in ruleDetails" :key="index">
<v-col
:class="{
'md-4': rule.width == 'large',
'md-3': rule.width == 'medium'
}"
>
</v-col>
</v-row
and rule.width = 'medium' right now.
It doesn't seem to take any effect.
Did I forget something ?

Answer 1

You can make it an array.
<v-row v-for="(rule, index) in ruleDetails" :key="index">
<v-col :class="[rule.width == 'large' && 'md-4', rule.width == 'medium' && 'md-3']">
</v-col>
</v-row
This resolves in :class="[false, 'md-3'] which Vue parses to <foo class="md-3" />
const rule = {
width: 'medium'
}
console.log([rule.width == 'large' && 'md-4', rule.width == 'medium' && 'md-3'])

Answer 2

You can use md attribute directly in <v-col> instead of class. To achieve this, You can apply one more property as value along with width in each object.
Demo (Run this code snippet in full page) :
new Vue({
el: '#app',
vuetify: new Vuetify(),
data: () => ({
ruleDetails: [{
width: 'small',
value: 2
}, {
width: 'medium',
value: 3
}, {
width: 'large',
value: 4
}]
}),
});
#app { padding: 1% 5% }
<script src="https://cdn.jsdelivr.net/npm/vue#2.x/dist/vue.js"></script>
<script src="https://cdn.jsdelivr.net/npm/vuetify#2.x/dist/vuetify.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/vuetify#2.x/dist/vuetify.min.css"/>
<div id="app">
<v-row v-for="(rule, index) in ruleDetails" :key="index">
<v-col :md="rule.value" style="background-color: yellow">
{{ rule.width }}
</v-col>
</v-col>
</v-row>
</div>