Xcode4 UML plugin?

I want to design my classes in UML. Currently am using ArgoUML, which is free, but not well integrated with Mac OS X, to say the least :-)

Googling around there's not much information

• any plugin开发者_如何学C/extension of XCode4 to do UML, like in Eclipse?
• third party apps that look well in Mac?
• any chance to get two ways code generation? Asking for too much? :-)

In my list of UML tools I don't have many Mac-specific tools. CanvasUML (free, only class diagrams) and MacA&D are the only completely designed for Mac. Others like VisualParadigm and MagicDraw have also a MAC version of their products