title: Vue.js - Restore input value if model rejects changes
body: <p>I have a text input that allow user to type a number with maximum of 3 digits after decimal point:</p>
  
  <pre><code>&lt;v-text-field type="text" :value="num" @change="changeNum($event)" /&gt;
  &lt;p&gt;{{ num }}&lt;/p&gt;
  
  ...
  
  export default {
    data: () =&gt; ({
      num: 0
    }),
    methods: {
      changeNum(e) {
        let v = parseFloat(e);
        if (!isNaN(v)) {
          this.num = parseFloat(v.toFixed(3));
        }
      }
    }
  };
  </code></pre>
  
  <p>If I type <code>'123.456'</code>, then <code>num = 123.456</code>.
  If I append text <code>'789'</code>, then input will contain <code>123.456789</code> but <code>num = 123.456</code>. So, user may think that the changes have been applied, but it is not...</p>
  
  <p>How can I force the input to update, if <code>changeNum</code> fails?</p>