Hello, I have recently been checking code sharing in KMM and have a question like how to know when to use expect and actual fun in common module KMM and when not to use it, like with some example usecase

Expect/actual is useful for bridging common code to a platform. Most of the time an interface is a better option. However if the common code needs to do the instantiation, expect/actual is better to use. Kotlin.Random in the std library is a good example of expect/actual. It wraps or type aliases the platform random number generator. One could certainly use an interface and pass in an RNG to a class or function as a dependency but the code may be cleaner in this case if the common code can create its own.

Another good example if you're using SQL Delight is the creation of DB driver

Thanks for the examples. Just want to confirm one thing like how do you get to decide that this logic should go into specific modules and this logic I would use interface(expect) and add implementations(actual) and keep them in common module, is it like only for UI/view layer I would keep in the specific module and for rest all other logical part or any other layer I would use expect and actual(which cannot work with one single impl)?

I default to interfaces because it makes unit testing easier. If the code gets too messy using an interface, I switch to an expect/actual class or function. My opinion is that expect/actual is useful but should be one of the least used options.