title: knockout validating multiple radio buttons
body: <p>I am using knockout and knockout validation in my project and I want to validate group of radio buttons if one of them is selected. In this fiddle you can see my html how it looks like and js too. </p>
  
  <pre><code>self.inputModel = ko.validatedObservable({
          discountAmount: ko.observable('').extend({
              required: {
                  onlyIf: function () {
                      return viewArray[1].bonusesFromCar() === 'yes';
                  }
              }
          }),
  </code></pre>
  
  <p><a href="https://jsfiddle.net/6ppqxqqh/" rel="nofollow noreferrer">https://jsfiddle.net/6ppqxqqh/</a> </p>
  
  <p>I am having problems with showing one message for those radio buttons... If you could help me somehow I would be gratefull.. </p>