title: How can I set f.select field as required - rails 5
body: <p>How can I set f.select field as required?</p>
  
  <p><code>:required =&gt; true</code> isn't working</p>
  
  <pre><code>&lt;div class="form-group"&gt;
  &lt;label&gt;Bedrooms&lt;/label&gt;
  &lt;%= f.select :bed_room, [["1",1], ["2",2], ["3",3], ["4",4], ["5",5], ["6",6], ["7",7], ["8",8], ["9",9], ["10+",10]], prompt: "Select...", class: "form-control", :required =&gt; true  %&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Tks in advance</p>