title: Validate form input fields in child component from a parent component with Vuelidate
body: <p>I am new to Vue Js and Vuelidate. Just tried to validate form input fields from a parent component like here: <a href="https://github.com/monterail/vuelidate/issues/333" rel="noreferrer">https://github.com/monterail/vuelidate/issues/333</a></p>
  
  <p>Child component in the parent:</p>
  
  <pre><code>&lt;contact-list ref="contactList" :contacts="contacts" @primaryChanged="setPrimary" @remove="removeContact" @ready="isReady =&gt; readyToSubmit = isReady"/&gt;
  </code></pre>
  
  <p>The method in the child:</p>
  
  <pre><code>computed: {
      ready() {
          return !this.$v.email.$invalid;
      }
  },
  watch: {
      ready(val) {
          this.$emit('ready', val);
      }
  },
  
  methods: {
      touch() {
          this.$v.email.$touch();
      }
  }
  </code></pre>
  
  <p>I'm calling the touch() method from the parent like so:</p>
  
  <pre><code>submit() {
              this.$refs.contactList.touch();
          },
  </code></pre>
  
  <p>But I get this error: </p>
  
  <p><code>Error in event handler for "click": "TypeError: this.$refs.contactList.touch is not a function".</code></p>
  
  <p>Any ideas? Thanks.</p>