title: Questions about drawRect in iOS
body: <p>Here is the thing: I have a view, which contains complicated content that need be redraw after related data updated. I use multiple views to implement this, more likely that one large view contains several subviews, and every subview may also have several subviews. All these views override their own drawRect: method.</p>
  
  <p>The question is that the complicated view takes large memory usage, and I want to know why drawRect: cause a large memory usage, so I can optimizing my view. </p>
  
  <p>Is there anyone give me a hand? Thanks.</p>