[UI Layer] #clean #architecture #android

BrowseCreaturesViewModel.kt

package com.raywenderlich.android.creatures.presentation.browse

open class BrowseCreaturesViewModel @Inject internal constructor(
    private val getCreatures: GetCreatures,
    private val creatureMapper: CreatureMapper) : ViewModel() {

  private val creaturesLiveData: MutableLiveData<Resource<List<CreatureView>>> = MutableLiveData()

  init {
    fetchCreatures()
  }

  override fun onCleared() {
    getCreatures.dispose()
    super.onCleared()
  }

  fun getCreatures(): LiveData<Resource<List<CreatureView>>> {
    return creaturesLiveData
  }

  fun fetchCreatures() {
    creaturesLiveData.postValue(Resource(ResourceState.LOADING, null, null))
    return getCreatures.execute(CreatureSubscriber())
  }

  inner class CreatureSubscriber: DisposableSubscriber<List<Creature>>() {

    override fun onComplete() { }

    override fun onNext(t: List<Creature>) {
      creaturesLiveData.postValue(Resource(ResourceState.SUCCESS,
          t.map { creatureMapper.mapToView(it) }, null))
    }

    override fun onError(exception: Throwable) {
      creaturesLiveData.postValue(Resource(ResourceState.ERROR, null, exception.message))
    }
  }

}

CreatureMapper.kt

package com.raywenderlich.android.creatures.presentation.mapper


open class CreatureMapper @Inject constructor(): Mapper<CreatureView, Creature> {
  override fun mapToView(type: Creature) =
    CreatureView(type.firstName, type.lastName, type.nickname, type.image, type.planet)
}

MainActivity.kt

class MainActivity : AppCompatActivity() {

  override fun onStart() {
    super.onStart()
    browseCreaturesViewModel.getCreatures().observe(this,
        Observer<Resource<List<CreatureView>>> {
          if (it != null) this.handleDataState(it.status, it.data, it.message) })
  }

  private fun handleDataState(resourceState: ResourceState, data: List<CreatureView>?,
                              message: String?) {
    when (resourceState) {
      ResourceState.LOADING -> setupScreenForLoadingState()
      ResourceState.SUCCESS -> setupScreenForSuccess(data)
      ResourceState.ERROR -> setupScreenForError(message)
    }
  }

}

Mapper.kt

package com.raywenderlich.android.creatures.presentation.mapper

interface Mapper<out V, in D> {
  fun mapToView(type: D): V
}