title: drawRect not being called in my subclass of UIImageView
body: <p>I have subclassed UIImageView and tried to override drawRect so I could draw on top of the image using Quartz 2D.  I know this is a dumb newbie question, but I'm not seeing what I did wrong.  Here's the interface:</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  
  @interface UIImageViewCustom : UIImageView {
  
  }
  - (void)drawRect:(CGRect)rect;
  @end
  </code></pre>
  
  <p>And the implementation:</p>
  
  <pre><code>#import "UIImageViewCustom.h"
  
  @implementation UIImageViewCustom
  
  - (id)initWithFrame:(CGRect)frame {
      if (self = [super initWithFrame:frame]) {
      }
      return self;
  }
  
  - (void)drawRect:(CGRect)rect {
      // do stuff
  }
  
  - (void)dealloc {
      [super dealloc];
  }
  @end
  </code></pre>
  
  <p>I set a breakpoint on <code>drawRect</code> and it never hits, leading me to think it never gets called at all.  Isn't it supposed to be called when the view first loads?  Have I incorrectly overridden it?</p>