UIView: how to do non-destructive drawing?

Question

My original question:

I\'m creating a simple drawing application and need to be able to draw over existing, previously drawn content in my d

Answer 1

This prevents your view from being erased before drawRect is done:

[self.layer setNeedsDisplay];

Also, I find it is better to do all the drawing in the drawRect method (unless you have a good reason not to). Drawing offscreen and transferring takes more time and adds more complexity then simply drawing everything once.