lmller / gof-in-kotlin Goto Github PK

I couldn't comment your post, so I'll try here.
Hi,
I really enjoyed reading your post, those very commonly used patterns look really great in Kotlin, so thank you for your work. I'm working for some time in Kotlin already, and I'm still coding more Java-like than Kotlin-like I suppose, your post has given me some tips. However, I've got a question about using extensions. Well, afaik those functions can be used to modify the class (decorate it) to which we do not have and access (Android classes for example). What is the reason to use extensions in for example Decorator pattern while probably we could just write some class methods and use them the same way?