title: iOS change button text to bold when highlighted or selected
body: <p>I need to set title to bold when it is highlighted or selected</p>
  
  <p>this is the code i use to generate button programmatically:</p>
  
  <pre><code>    UIButton *pagerButton = [UIButton buttonWithType:UIButtonTypeCustom];
      [pagerButton setFrame:CGRectMake(offsetX, 10, 30, 30)];
  
      [pagerButton setTitle:pageNumber forState:UIControlStateNormal];
      [pagerButton setTitleColor:[UIColor purpleColor] forState:UIControlStateNormal];
  </code></pre>
  
  <p>i can't find any property to set title's font or change it to bold forState:UIControlStateHighlighted</p>