RxJava ViewModelScope

ViewModelScope.kt

class TestViewModel : MyViewModel() {

    init {
        scope.launch(
            Observable.just("10")
                .subscribe { println("Something") }
        )

        Observable.just("10")
            .doOnNext { println("something") }
            .launchIn(scope)

        // beware, still possible to run without scope
        Observable.just("10")
            .subscribe { println("Something") }
    }
}

abstract class MyViewModel {

    private val observers = mutableMapOf<String, Closeable>()

    fun onDestroy() {
        observers.values.forEach(Closeable::close)
        observers.clear()
    }

    fun setObserver(key: String, value: Closeable) {
        observers[key] = value
    }

    fun getObserver(key: String): Closeable? {
        return observers[key]
    }
}

interface MyScope : Closeable {

    fun launch(job: Disposable)
}

private const val TAG_SCOPE = "TAG_SCOPE"
val MyViewModel.scope: MyScope
    get() {
        val scope = getObserver(TAG_SCOPE) as? MyScope
        if (scope != null) {
            return scope
        }

        val newScope = object : MyScope {
            val compositeDisposable = CompositeDisposable()

            override fun launch(job: Disposable) {
                compositeDisposable.add(job)
            }

            override fun close() {
                compositeDisposable.clear()
            }
        }
        this.setObserver(TAG_SCOPE, newScope)
        return newScope
    }

fun <T> Observable<T>.launchIn(scope: MyScope) {
    return scope.launch(this.subscribe())
}