LiveData meets RxJava

dependency.gradle

compile "android.arch.lifecycle:reactivestreams:$archVersion"

repo1.kt

class PostRepo(private val api: Api) {    
  
  private sealed class Command {        
    class Reset(val size: Int) : Command()        
    class LoadMore(val position: Int, val size: Int) : Command()    
  }    
  
  private var itemIds = emptyList<Long>()    
  private val commands = MutableLiveData<Command>()    
  
  val posts: LiveData<List<Item>> = commands.switchMap {
    ...
  }
  
  fun load(size: Int) {   
    itemIds = emptyList()       
    commands.value = Command.Reset(size)    
  }    
  
  fun loadMore(size: Int) {       
    commands.value = Command.LoadMore(posts.value?.size ?: 0, size)  
  }
}

switchmap.kt

  fun <T, R> LiveData<T>.switchMap(f: (T) -> LiveData<R>): LiveData<R> = Transformations.switchMap(this, f)

switchmap2.kt

val posts: LiveData<List<Item>> = commands.switchMap { 
  val command = it   
  LiveDataReactiveStreams.fromPublisher<List<Item>> {   
    when (command) {           
      is Command.Reset -> {                 
        getFirst(command.size)           
      }          
      is PostRepo.Command.LoadMore -> {     
        getMore(command.position, command.size)     
      }        
    }
    .subscribeOn(Schedulers.io())    
    .observeOn(AndroidSchedulers.mainThread())         
    .toFlowable()         
    .subscribe(it)    
  }
}

ViewModel.kt

class MainViewModel(app: Application) : AndroidViewModel(app) {    
  private val postRepo = getApplication<App>().postRepo  
  private val LOAD_ITEM_COUNT = 15    
  
  fun getPosts(): LiveData<List<Post>> {        
    return postRepo.posts.map {                     
      it.map { Post(it.id, it.title, it.url) } 
    }    
  }    
  
  fun refresh() {         
    postRepo.load(LOAD_ITEM_COUNT)  
  }    
  
  fun loadMore() {          
    postRepo.loadMore(LOAD_ITEM_COUNT)    
  }
}