Since the model class tool was excluded in Xcode 4, what other alternatives could you recommend for UML modeling tools for Objective-C?
http://projects.gnome.org/dia/
OmniGraffle runs UML diagrams.
However, it does not generate code.
You can use yEd ... not the best solution and not generate graphs like OmniGraffle, but at least it can export to SVG and use GraphML files to store data. (and this is the board)
http://www.yworks.com/en/products_yed_helpresources.html
I would recommend Visual Paradigm , which can do this very quickly with a few clicks.
Drop the document folder containing the Xcode project file onto the OmniGraffle icon on the dock, OmniGraffle will generate UML diagrams.