StateLiveData2.kt

class StateLiveData<T> : MutableLiveData<T>() {

    val state = EventLiveData<State>()

    init {
        clearState()
    }

    fun post(observable: Observable<T>, successOnFirstValue: Boolean = true): Disposable {
        postLoading()
        return observable.subscribeOn(Schedulers.io())
                .subscribe({
                    if (successOnFirstValue) {
                        postValueAndSuccess(it)
                    } else {
                        postValue(it)
                    }
                }, { postError(it) }, { postSuccess() })
    }

    private fun postValueAndSuccess(value: T) {
        super.postValue(value)
        postSuccess()
    }

    fun clearState() {
        state.postValue(State.Idle)
    }

    fun postLoading() {
        state.postValue(State.Loading())
    }

    fun postSuccess() {
        state.postValue(State.Success())
    }

    fun postError(throwable: Throwable) {
        state.postValue(State.Error(throwable))
    }

    fun postState(s: State) {
        state.postValue(s)
    }

    /**
     * state of this live data, can be extended
     */
    open class State {

        object Idle : State()

        open class Loading : State()

        open class Success : State()

        open class Error(val error: Throwable) : State()
    }
}