アーキテクチャの試し書き

mvvm_flux.kt

class User
class Program
class MergedState(u: User, p: Program)

interface UserRepository {
  suspend fun getUser(): User
}

interface ProgramRepository {
  suspend fun getPrograms(): List<Program>
}

fun <X, Y, Z> zip(source1: LiveData<X>, source2: LiveData<Y>, merge: (X, Y) -> Z): LiveData<Z> {
  return MediatorLiveData<Z>().apply {
    addSource(source1) { s1 ->
      val s2 = source2.value
      if (s1 != null && s2 != null) postValue(merge(s1, s2))
    }
    addSource(source2) { s2 ->
      val s1 = source1.value
      if (s1 != null && s2 != null) postValue(merge(s1, s2))
    }
  }
}

sealed class Action {
  class UserAction(val user: User) : Action()
  class ProgramsAction(val programs: List<Program>) : Action()
}

interface Dispatcher {
  fun dispatch(action: Action)
}

class UserStore {
  private val _user = MutableLiveData<User>()
  val user: LiveData<User>
    get() = _user

  fun on(action: Action.UserAction) {
    _user.postValue(action.user)
  }
}

class ProgramsStore {
  private val _programs = MutableLiveData<List<Program>>()
  val program: LiveData<List<Program>>
    get() = _programs

  fun on(action: Action.ProgramsAction) {
    _programs.postValue(action.programs)
  }
}

class UserActionCreator {
  lateinit var userRepository: UserRepository

  fun getUserAction(): Action {
    return Action.UserAction(userRepository.getUser())
  }
}

class ProgramsActionCreator : BaseActionCreator() {
  lateinit var dispatcher: Dispatcher
  lateinit var programsRepository: ProgramRepository

  fun getProgramsAction(): Action {
    return Action.ProgramsAction(programsRepository.getPrograms())
  }
}

class ActivityScopeViewModel : BaseViewModel() {

  lateinit var dispatcher: Dispatcher
  lateinit var actionCreator: UserActionCreator

  fun getUser() {
    launchWithLoading {
      dispatcher.dispatch(actionCreator.getUserAction())
    }
  }
}

class FragmentScopeViewModel : BaseViewModel() {

  lateinit var dispatcher: Dispatcher
  lateinit var userStore: UserStore
  lateinit var programsStore: ProgramsStore
  lateinit var actionCreator: ProgramsActionCreator

  val fragmentState: LiveData<List<MergedState>>
    get() = zip(userStore.user, programsStore.program) { u, p ->
      p.map { MergedState(u, it) }
    }

  fun getPrograms() {
    launchWithLoading {
      dispatcher.dispatch(actionCreator.getProgramsAction())
    }
  }
}

class DemoActivity : Activity() {
  lateinit var activityScopeViewModel: ActivityScopeViewModel

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    activityScopeViewModel.getUser()
  }
}

class DemoFragment : BaseFragment() {

  lateinit var fragmentScopeViewModel: FragmentScopeViewModel

  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    fragmentScopeViewModel.fragmentState.observe(this, Observer {
      // bindingにわたすなり, RecyclerViewの構築を行うなり
    })
    fragmentScopeViewModel.getPrograms()
  }
}