UML Class Diagram for Xcode (Not Omnigraffle)

I finally finished my application, everything works fine and I have implemented all the functionality that I need.

So now I started making documentation. Problem - I need a UML class diagram. To make matters worse, I have run out of my trial license for OmniGraffle. Since this is a project for my research, I don't want to spend $ 100 (which is quite a lot in my country) on software that I can't use for a long time.

Is there any software that can generate UML class diagrams for Xcode other than OmniGraffle? For most diagrams, I use a clear diagram, but it doesn't seem to have a UML generator.

Thanks in advance!