kotlin-multiplatform-expect-actual

Declare a semantic expect function, value, or class in commonMain and provide platform-specific actual implementations in androidMain and iosMain. Keep the common signature free of platform types like Context or UIViewController so callers describe intent, not platform mechanics.

Use a common interface with platform bindings when the implementation needs injected dependencies, lifecycle ownership, runtime selection, or test fakes. Reserve expect/actual for simple compile-time platform specialization without those requirements.

Keep platform-specific composables at leaf nodes, pass Modifier through expected composables, and hide native view lifecycle inside the platform actual using interop containers like AndroidView or UIKitView. Never put platform types in commonMain composable signatures.

No, commonMain signatures must reject platform types such as Context, Activity, Uri, Bundle, or UIViewController. If an operation needs an Activity or lifecycle owner, define a common interface and supply the implementation from platform code instead of an expect class.

Changes often break other targets when actuals are updated for only one platform or common signatures leak platform vocabulary. Compile every affected source set after each change and keep business branching in common code so actuals stay thin translation layers.