title: How to create an extension of UIView with a variable string parameter in Swift?
body: <p>I want all my views have a property stored like a tag, but it has to be type of String. So I tried using an extension for it. </p>
  
  <p>But I got the error saying extensions my not contain stored properties.</p>
  
  <p>The question is, how to store a string in each UIView in my app like a tag?</p>
  
  <p>Thanks!</p>