Derive a class from UIAppearance for custom views

I'm trying to "extend" the properties offered by the default implementation of UIAppearance.

I've been able to expose some properties in the standard UIKit objects (e.g. add a "Radius" property for UIButton) by following the article at this site: kipters.dev/posts/ios-custom-uiappearance/

Instead I haven't been able to expose the properties of custom views (e.g. a view derived from UIView, containing some internal objects, that I'd like to configure through some properties exposed by the custom view).

I tried to derive a class from UIViewAppearance but I couldn't use it in my custom view (I overrode the Appearance static property, but I couldn't make it work).

Any suggestion?