OS X Cocoa Auto Layout hidden elements

Question

I am trying to use the new Auto Layout in Lion because it seems quite nice. But I can not find good information about how to do things. For example:

I have two labels:

Answer 1

This category makes collapsing Auto Layout constrained views really simple:

https://github.com/depth42/AutolayoutExtensions

I just added it to a project and it works great.