title: How can I bold part of a string in Swift?
body: <p>If I create a label like this: </p>
  
  <pre><code>var label = UILabel(...)
  label.text = first_name + ", " + age
  self.view.addSubview(label)
  </code></pre>
  
  <p>How can I change the age of the label to bold, but keep the first_name normal weight?</p>