UML how to represent a class concern/module/extension

Question

I am talking about concern/module/extensions as they exist in Ruby and Swift for example.

A Ruby module is something that a class can include (= add the module functions as its own instance methods) or extend (add the module functions as its own class methods).

A swift extension is also an add-on for class, typically when you want to add a functionality you would first define the prototype, then implement it in an extension.

(please correct me if I'm wrong)

How would you represent such a Ruby module/Swift extension in UML, and its link to the class it is included in/it extends ?

Answer 1

I also don't know a standard for this, but would model it like this:

A Realize relation with an <<import>> stereotype. Maybe the Realize is too strong in the context and a simple Dependency but still with that stereotype would be better.

Not everything is available natively in UML. But like in any language, if you don't have a single word for a thing you can make constructs that describe the thing. You are rather free in choosing your vocabulary. Only you should be consistent in the domain where you use such a paraphrase.