title: How can I use Vuelidate to validate a <select> input
body: <p>Hi I am trying to validate a  input with Vuelidate, I have seen in other posts but it's just question about text inputs but I need a select input validation, my code is:</p>
  <p>Html Code:</p>
  <pre><code>&lt;div class=&quot;form-group&quot;&gt;
     &lt;label for=&quot;exampleInputEmail1&quot;&gt;Tipo de Caja&lt;/label&gt;
     &lt;select class=&quot;form-control&quot; 
     v-model=&quot;$v.form.cashier_type_id.$model&quot;
     :class=&quot;{
         'is-valid':!$v.form.cashier_type_id.$error &amp;&amp; $v.form.serie.$dirty,
         'is-invalid':$v.form.cashier_type_id.$error &amp;&amp; $v.form.serie.$dirty
     }&quot;
     id=&quot;exampleFormControlSelect1&quot;&gt;
     &lt;option value=&quot;&quot;&gt;- Seleccione -&lt;/option&gt;
     &lt;option value=&quot;2&quot;&gt;Automática&lt;/option&gt;
     &lt;option value=&quot;3&quot;&gt;Electrónica&lt;/option&gt;
     &lt;option value=&quot;1&quot;&gt;Manual&lt;/option&gt;
    &lt;/select&gt;
  &lt;/div&gt;
  </code></pre>
  <p>My Vue code:</p>
  <pre><code>      validations: {
          form: {
              name: {
                  required,
                  minLength: minLength(2)
              },
              serie: {
                  required,
                  minLength: minLength(2)
              },
              cashier_type_id: {
                  required
              }
          }
      }
  </code></pre>
  <p>I added required but the thing is that it does not change the color to green when I select the option so I wonder how can I do the validation?</p>
  <p>Thanks</p>