working with large existing native codebases (Swif...

# multiplatform

[Wes Cook]

working with large existing native codebases (SwiftUI, Jetpack Compose for all new stuff), I want to refactor native ViewModels into KMP code. Should I use KMP’s ViewModel or start with a library like moko’s MVVM?

[Wes Cook]

the docs for KMP ViewModel seems targeted at Compose Multiplatform

[Wes Cook]

and moko MVVM predates the KMP ViewModel, right?

[Pablichjenkov]

Just an opinion, keep the ViewModel in swift and share kmp from the domain layer down, UseCases in CLEAN terminology.
Cabling these ViewModels(any library) to swiftui requires a lot of work. Easier to share a UseCase that has a plain(not suspend or FlowT) function that returns a sealed ResultT

[Joel Denke]

I would use androidx Viewmodel. Get a feeling Jetbrains and Google streamline a lot and going into a clean direction. Also its easier for compose code align into. But depends ofc how swift ui code looks like.

[François]

@Wes Cook using the KMP viewmodel is possible with iOS, but with some helper to write.
Look at my exploration.

[Wes Cook]

thank you for your responses. I appreciate you sharing your repo @François. Looks like a good place to start.

[François]

Yes, It’s a starting point, I don’t want to impose something,
The management of the KMP VM’s lifecycle on iOS is totally new.

[Pablichjenkov]

I find two tricky things when sharing at the ViewModel level:
1- ViewModel lifecycle management from iOS.
2- Transforming events from STateFlowT to swiftui @Observable State.

[Wes Cook]

noob question: if you wrap your KMP ViewModel as a ObservableObject, what part of the lifecycle concerns does that leave to me?

class SharedViewModel<VM: ViewModel>: ObservableObject {

[François]

By wrapping, the lifecycle of KMP VM is sync with the ObservableObject lifecycle (which is also used for SwiftUI VM).

[François]

Also, you need to manage some case like this one.

[François]

like SwiftUI async method but kind of differently.

[Pablichjenkov]

But will that automatically call ViewModel::onCleared() once the swiftui component/screen is detached/unmounted?

[François]

Yes, that’s the goal.