I just instantiate the class once, and then I am able to call any extension function on it.

in order to read/write class properties from extension functions, is the only requirement to define them as “internal” instead of “private”?

My suggestion for creating extension functions is to always use only public API that is available to you from that class. In that case extension function would be exactly that - extending your core API with additional utility. For example: you have

List

collection. It has

.get()

method to get element of a list. To get last element of list you could write:

list.get(list.size - 1)

. So, you can achieve your goal using “core” API of a class. But with extension function you can extract this code, to reuse is later as as

list.last()

. Your extension function in this case uses only public API (method

get()

)

I am using it inside a KMP shared module

“internal” is still better than “public”

My use case is a class that holds the state for the application. And the extension functions would be the “state reducers”, the functions that modify the state.

I find it convenient to group them in separate files, depending on which is the section of the app they are dealing with

if you are interested, you can find more info on the last page of my 3-page article:

with this approach, it’s also very easy to test them, just by injecting/replacing a mock repository