title: Swift Protocol conform to two specific classes only
body: <p>I want to make a protocol which can only be conformed by UIlabels and UIButton, is there a way ?</p>
  
  <p>Example :</p>
  
  <pre><code>protocol MyProtocol {
      func setTextValue()
  }
  </code></pre>
  
  <p>I want MyProtocol to only be acessed by UILabel and UIButton and no other class</p>