CALayer Internals: Contents

Why CALayer’s contents property is typed as id, and the neat trick that makes possible. Spoiler: you can clone a layer’s contents — even a CABackingStore — without ever touching a CGImageRef.

CALayers v. CGLayers, or, Which Layer, Player?

CALayer and CGLayer sound related. They’re not. Here’s why you should ignore CGLayer on iOS. A quick breakdown of what each layer type actually does and why CGLayer’s desktop advantages don’t carry over.