title: Check if NSString is HTML string on non-HTML?
body: <p>I am using a UITextView to display text on a screen. I also want to display HTML text in the same TextView. What I want is, when the string contains any HTML data then it should be displayed according to HTML formatter otherwise textview should use the font defined by me.</p>
  
  <p>Here is the code I am using to display the HTML text in the textview:</p>
  
  <pre><code>NSString *htmlString = promotion.content;
  NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType } documentAttributes:nil error:nil];     
  self.promotionTextView.attributedText = attributedString;
  </code></pre>
  
  <p>I just want to check if the string that I am receiving in the htmlString contains any html data or not.
  How I can do that?</p>