title: drawRect and addSubview: custom drawing affects which views?
body: <p>If I have a custom subclass of <code>UIView</code> that implements <code>drawRect</code> and controller methods use <code>addSubview</code> to create a view hierarchy in this custom view, how does <code>drawRect</code> interact with these subviews? Does it recreate the entire subclass's view hierarchy from scratch and remove any existing subviews? Or does it ignore subviews and only redraw a particular view/subview?</p>
  
  <p>Would it be acceptable to programmatically add and remove subviews within <code>drawRect</code>?</p>