title: Vue show/hide error based on result of @change function
body: <p>I would like to conditionally render an error message based on the email address a user enters when they register.  If the email is in use, show the error. If the email is not in use, proceed with registration.  What I have so far is after the user clicks out of the text field, an on change event calls a function that returns true if the email is available.  </p>
  
  <pre><code>&lt;v-flex xs12&gt;
    &lt;v-text-field
      autocomplete="ignoreautocompleteemail"
      :rules="emailRules"
      append-icon="email"
      v-model="person.email"
      outlined
      @change="checkEmail(person.email)"
      name="email address"
      label="Email Address"
      type="text"
    &gt;&lt;/v-text-field&gt;
  &lt;/v-flex&gt;
  </code></pre>
  
  <p>I'm not familiar enough with vue yet to understand how to do something with the result of the @change event. </p>
  
  <p>How can I use the value returned from @change to conditionally render an error message in my text field?</p>
  
  <p>Many thanks in advance,
  Chappie Johnson</p>