Using Opacity-generated layers in Quartz 2d instead of drawing to the view's layer

Firstly, be gently with me. I'm new to Objective C and iOS programming. I've just purchased a copy of Opacity and I'm playing around with layers. My only grade A success so far is to design and successfully generate my own design of a calculator - so I haven't got that far!

Specifically, I want to know how to use Opacity CALayer subclasses to 'replace' the backing layer on a UIView. Adding sublayers to the existing view layer is obvious enough - and I've managed to get that working - but how do I use an Opacity CALayer subclass to provide the initial content of the view's backing layer? I've tried copying the drawInContext code from an Opacity subclass into drawRect on my UIView subclass that hosts the proxy view for the controllers' 'view' property but (for some reason I can't fathom) that didn't work.

I assume that the view's original backing layer is item '0' in the layer array? My ultimate goal is to have just my layers behind the view without having to 'ignore' the original one.

If there's a chance that Dr Brad Larson might read this;... I've watched your Quartz 2D and animation videos over and over and I've read all of the copies of your course notes that I can lay hands on but all the examples I've found start with an image already in the hosting view - onto which more layers are added, which isn't really what I"m after. I've also read the Big Nerd Ranch Guide and got all of Conway and Hillegass's example code too but - I'll be darned - they also start with an image already in the view!

If any one can help me out - just point me at the relevant documentation, please don't bother writing huge tranches of code here - I'd be seriously grateful.

VV. PS: I'm deliberately NOT using IB yet as I wan开发者_JS百科t to grip the underlying mechanics of Cocoa Touch first and I won't use dot notation on principal :-). (See my profile!).

The trick is to override the view's class method 'layerClass' to be the base layer sub-class that's needed before nailing other layers into the hierarchy. This builds the view's base (implicit) layer when the view is instantiated and then I can slap my other layers down afterwards.

This is a fun game. I'll get the mind-set soon!

This technique differs markedly from the same requirement using NSViews which have a 'setLayer' instance method that can be used to change the implicit layer AFTER instantiation. An expensive procedure not offered on a lightweight object like a UIView.