title: Create ControlProperty for custom UIControl
body: <p>Is it possible to make extension of structure Reactive, where base class is my custom control inherited from UIControl?</p>
  
  <p>When I'm trying following code:</p>
  
  <pre><code>extension Reactive where Base: CustomControl {
  
      public var value: ControlProperty&lt;CGFloat&gt; {
  
          return CustomControl.rx.value(
  
              self.base,
  
              getter: { customControl in
                  customControl.customProperty
              },
              setter: { customControl, value in
                  customControl.customProperty = value
              }
          )
      }
  }
  </code></pre>
  
  <p>I'm getting following error:</p>
  
  <pre><code>Instance member "value" cannot be used on type 'Reactive&lt;CustomControl&gt;'
  </code></pre>
  
  <p>I will be grateful if you provide me any explanation.</p>