title: Vuetify how to add/remove rule dynamically
body: <p>I'm using vuetify validation, and i have three date fields: <strong>Month</strong>, <strong>From</strong>, <strong>To</strong>. I need to add required rule according to the following:</p>
  <ul>
  <li>If <strong>Month</strong> selected - <strong>From</strong> and <strong>To</strong> not required.</li>
  <li>If any of <strong>From</strong> or <strong>To</strong> selected - <strong>Month</strong> not required.</li>
  </ul>
  <p>I tried computed() method, to check if <strong>From</strong> or <strong>To</strong> are null, but it seems like :rules set once, and then not change.</p>
  <pre><code>computed: {
      monthRules() {
        return this.searchForm.from ? [] : [factory.required()];
      },
  </code></pre>
  <p>Here's some code</p>
  <pre><code>&lt;date-field
    ref=&quot;month&quot;
    v-model=&quot;searchForm.month&quot;
    :rules=&quot;monthRules&quot;
  &gt;
  &lt;/date-field&gt;
  
  &lt;date-field
    ref=&quot;from&quot;
    v-model=&quot;searchForm.from&quot;
    @input=&quot;validateTo&quot;
    :rules=&quot;fromRules&quot;
  &gt;
  &lt;/date-field&gt;
      
  &lt;date-field
    ref=&quot;to&quot;
    v-model=&quot;searchForm.to&quot;
    :rules=&quot;toRules&quot;
  &gt;
  &lt;/date-field&gt;
            
  </code></pre>
  <pre><code>monthRules: [factory.required()],
  fromRules: [],
  toRules: [
    *some rules from factory here*
  ],
  </code></pre>
  <h3>factory</h3>
  <pre><code>required() {
      return v =&gt; !!v || 'Field is required';
  },
  
  </code></pre>
  <p>Is it possible to dynamically build an array of rules? Or is there a better way</p>