title: KVC vs fast enumeration
body: <p>Which of the following is faster and why?</p>
  
  <pre><code>CGFloat sum = 0;
  for (UIView *v in self.subviews)
      sum += v.frame.size.height;
  </code></pre>
  
  <p>or </p>
  
  <pre><code>CGFloat sum = [[self.subviews valueForKeyPath:@"@sum.frame.size.height"] floatValue];
  </code></pre>