title: How to know if rule is failing in vuetify's v-text-field?
body: <p>How do I know if a "rule" is failing in vuetify? I have a text field</p>
  
  <pre><code>&lt;v-text-field label="Friendly URL" :rules="[rules.friendlyUrl]" v-model="friendlyUrl"&gt;&lt;/v-text-field&gt;
  </code></pre>
  
  <p>And my rules definition:</p>
  
  <pre><code>data () {
    return {
      rules:{
        friendlyUrl(value){
          console.log('validating value');
          if (/^[a-z0-9\-]*$/.test(value)){
            return true;
          }
          return 'only lowercase letters, numbers and dashes are allowed'
        }
      }
    }
  </code></pre>
  
  <p>I want to "watch" something to know if my rule has failed or not. That way I can disable a submit button until all rules have passed.</p>
  
  <p>Bonus points if you know how to set this up for multiple text fields.</p>