title: CALayer & drawRect
body: <p>In <a href="http://developer.apple.com/library/ios/#documentation/windowsviews/conceptual/viewpg_iphoneos/WindowsandViews/WindowsandViews.html" rel="noreferrer">View and Window Architecture</a> is stated, quote: </p>
  
  <p><em>Views work in conjunction with Core Animation layers to handle the rendering and animating of a view’s content. Every view in UIKit <strong>is backed by a layer object</strong> (usually an instance of the CALayer class), which manages the backing store for the view and handles view-related animations.</em> </p>
  
  <p>Farther in the "The View Drawing Cycle" section is stated:</p>
  
  <p><em>The UIView class uses an on-demand drawing model for presenting content. When a view first appears on the screen, the system asks it to draw its content. <strong>The system captures a snapshot of this content</strong> and uses that snapshot as the view’s visual representation.</em></p>
  
  <p>Does that mean, that the content drawn in a view in its drawRect method call, is captured in a snapshot in saved in its backing core animation layer?</p>
  
  <p>If not, where do this content snapshot "reside"?</p>
  
  <p>If not, does that mean that CALayer is used to render "static" content, content that doesn't change very often, and drawRect is used to render content that changes often, for example in a game app?</p>
  
  <p>p.s.</p>
  
  <p>The questions are not related to any particular code implementation.</p>
  
  <p>I just want to understand the ios view-layer architecture.</p>