iOS: Using UIView's 'drawRect:' vs. its layer's delegate 'drawLayer:inContext:'

Question

I have a class which is a subclass of UIView. I am able to draw stuff inside the view either by implementing the drawRect method, or by implementin

Answer 1

drawRect should only be implemented when absolutely needed. The default implementation of drawRect includes a number of smart optimizations, like intelligently caching the view's rendering. Overriding it circumvents all of those optimizations. That's bad. Using the layer drawing methods effectively will almost always outperform a custom drawRect. Apple uses a UIView as the delegate for a CALayer often - in fact, every UIView is the delegate of it's layer. You can see how to customize the layer drawing inside a UIView in several Apple samples including (at this time) ZoomingPDFViewer.

While the use of drawRect is common, it's a practice that has been discouraged since at least 2002/2003, IIRC. There aren't many good reasons left to go down that path.

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