title: How do I dynamically set validations fields in vuelidate
body: <p>I'm using VueJS2 with <a href="https://github.com/monterail/vuelidate" rel="noreferrer">vuelidate</a> library. I can validate the fields based on the validation objects. The validation will execute during computed time. But My validations objects is fixed, instead of dynamic. I have some fields will hide based on the selection.</p>
  
  <pre><code>import { validationMixin } from 'vuelidate'
  import { required, maxLength, email } from 'vuelidate/lib/validators'
  
  export default {
  mixins: [validationMixin],
  validations: {
    company_name: { required },
    company_position_title: { required }
  },
  methods: {
    submit(){
      this.$v.touch();
      if(this.$v.$invalid == false){ 
        // All validation fields success
      }
    }
  }
  }
  </code></pre>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;v-select
    label="Who are you?"
    v-model="select" // can be 'company' or 'others'
    :items="items"
    :error-messages="selectErrors"
    @change="$v.select.$touch();resetInfoFields();"
    @blur="$v.select.$touch()"
    required
  &gt;&lt;/v-select&gt;
  
  &lt;v-text-field
    label="Company Name"
    v-model="company_name"
    :error-messages="companyNameErrors"
    :counter="150"
    @input="$v.companyName.$touch()"
    @blur="$v.companyName.$touch()"
    v-show="select == 'Company'"
  &gt;&lt;/v-text-field&gt;
  
  &lt;v-text-field
    label="Company Position Title"
    v-model="company_position_title"
    :error-messages="companyPositionErrors"
    :counter="150"
    @input="$v.companyPosition.$touch()"
    @blur="$v.companyPosition.$touch()"
    v-show="select == 'Company'"
  &gt;&lt;/v-text-field&gt;
  
  &lt;v-btn @click="submit"&gt;submit&lt;/v-btn&gt;
  </code></pre>
  
  <p><strong>Problem</strong></p>
  
  <p>When I select 'other' option and click submit, the <code>this.$v.$invalid</code> is still true. It should be false as there is no validation fields required. 
  When I select 'company', that two fields must required and validated.</p>