title: Equivalent of -viewDidAppear for CCLayer?
body: <p><strong>Question:</strong><br />
  In the realm of cocos2d for iPhone, what's the equivalent of UIKit's -viewDidAppear callback for CCLayer? </p>
  
  <p>*And if no equivalent exists (<em>as seems to be the case in the docs</em>), what's your recommended way knowing when a CCLayer has been rendered?</p>