title: Can`t draw in CAlayer
body: <p>HI All.</p>
  
  <p>I have subclass of UIScrollView. IN this class I have added some <code>imageView.layer</code> to <code>self.layer</code>. And when I call <code>[imageView.layer setNeedsDisplay]</code> my implemented delegate never called. </p>
  
  <pre><code>-(void)drawLayer:(CALayer*)layer :(CGContextRef)context 
  </code></pre>
  
  <p>I`ve also set </p>
  
  <pre><code>imageView.layer.delegate = self
  </code></pre>
  
  <p>Could anyone tell me where I must set delegate function to make this to work.</p>
  
  <p>Thank you for advance. </p>