ViewStates Example

FragmentRenderViewState.kt

 override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        FeedCommentsViewModel().feedViewState.observe(viewLifecycleOwner, Observer { viewState ->
            render(viewState)
        })
    }

    private fun render(viewState: FeedCommentsViewState) {
        viewState.apply {
          renderLoading(feedDetailsState.isLoading)
        }
    }

    private fun renderLoading(isLoading:Boolean) {
        if(isLoading){
            //show some view
        }else{
            //hide some view
        }
    }

state.kt

sealed class States{
    data class State1(val somePara :Int):States()
    data class State2(val somePara :Int):States()
    data class State3(val somePara :Int):States()
}
data class FeedCommentsViewState(
    val feedDetailsState: FeedViewState = FeedViewState(),
    val commentsViewState: CommentViewState = CommentViewState()
)

data class FeedViewState(
    override val isLoading: Boolean = false,
    override val payload: FeedDetails = FeedDetails(),
    override val error: Throwable? = null
) : BaseViewState<FeedDetails>()

data class CommentViewState(val isEmpty: Boolean = false, val commentIsUploading: String? = null) :
    BaseViewState<CommentDetail>()

abstract class BaseViewState<T>(
    open val isLoading: Boolean = false,
    open val payload: T? = null,
    open val error: Throwable? = null
)

UsingStateViewModel.kt

class FeedCommentsViewModel() {
    val feedViewState: MutableLiveData<FeedCommentsViewState> = MutableLiveData()

    init {
        feedViewState.value = FeedCommentsViewState()

        //start request feed
        feedViewState.postValue(
            currentState().copy(
                feedDetailsState = currentState().feedDetailsState.copy(
                    isLoading = true
                )
            )
        )
        feedViewState.postValue(
            currentState().copy(
                feedDetailsState = currentState().feedDetailsState.copy(
                    payload = FeedDetails(),
                    isLoading = false
                )
            )
        )

        feedViewState.postValue(
            currentState().copy(
                commentsViewState = currentState().commentsViewState.copy(
                    commentIsUploading = "commentId",
                    isEmpty = false
                )
            )
        )


    }


    fun currentState() = feedViewState.value!!
}