title: Swift 3.0 get the height of html string in UILABEL
body: <p>I have list on rows on UITableView, and each row contain html string come from the apis, I am using </p>
  
  <pre><code> let str = try NSMutableAttributedString(data: d,
                                                      options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
                                                      documentAttributes: nil)
  </code></pre>
  
  <p>But I cannot get the real height of each html string? I tried to use Label.sizeThatFits but it did not work.</p>
  
  <p>How can I get the real height of html string from UILabel?</p>
  
  <p>Thanks</p>