Say there's a class in a library: ```interface Foo...

# getting-started

[dave08]

Say there's a class in a library:

interface FooBase<S> {
  val state: Flow<S>
}

public abstract class Foo<S>(): FooBase<S> {
  override val state: Flow<S> get() { ... }
}
// I'd like to have this as a state flow (I need to pass this to users of MyFoo, because there could be other implementations... but they need StateFlow, so I can't use Foo):
abstract class MyFooBase : Foo<Bar> {
   override abstract val state: StateFlow<Bar>
}

class MyFoo : MyFooBase<Bar> {
  override val state: StateFlow<Bar> by lazy {
    super.state...stateIn(...)
  }
}

But I get an error abstract-member-cannot-be-access-directly-kotlin ... is there any way to do this?

[Sam]

I would approach this using association rather than inheritance. Instead of inheriting from Foo, can you just make a new class that implements FooBase and delegates to a private instance of Foo?

[dave08]

Foo is an abstract class.... so I'd have to implement it and delegate to it... Foo is really https://github.com/freeletics/FlowRedux/blob/main/flowredux/src/commonMain/kotlin/com/freeletics/flowredux/dsl/FlowReduxStateMachine.kt

[dave08]

That's a good idea, just wondering how to do it with the least boilerplate...

[Sam]

Does Kotlin’s built-in delegation help? Building on the example code you shared it would look something like this:

class MyFoo<S>(delegate: FooBase<S>, scope: CoroutineScope): FooBase<S> by delegate {
    override val state: StateFlow<Bar> by lazy {
        delegate.state.stateIn(scope)
    }
}

[dave08]

delegate { } imported:
import androidx.compose.ui.text.platform.EmojiCompatStatus.delegate.... 😂

[Sam]

😄

[Sam]

Maybe my syntax isn’t quite right

[dave08]

I'd have to use by object : FlowReduxStateMachine { ... }

[dave08]

Actually, I could just make a wrapper class around the SM and just delegate the functionality I want to expose to the wrapped class w/o Kotlin's delegation (which copies over all the functionality per se...). Thanks for the idea!