Provider Template - method

@Suppress("UNCHECKED_CAST")
fun <T: ViewModel> VMProvider(
    owner: ViewModelStoreOwner,
    instance: ViewModel
): T {
    val factory = object : ViewModelProvider.Factory {
        override fun <T : ViewModel> create(modelClass: Class<T>): T {
            return if (modelClass.isAssignableFrom(instance.javaClass)) {
                instance as T
            } else {
                throw IllegalArgumentException()
            }
        }
    }
    return ViewModelProvider(owner, factory).get((instance as T).javaClass)
}

// use
val viewModel by lazy {
		val tempViewModel = TempViewModel(TempUseCase(TempRepository()))
		VMProvider(this@Activity, tempViewModel)
} 

Provider Template - member variable

private val viewModel by lazy {
    val repository: TempRepository = TempRepositoryImpl()
    val factory = object : ViewModelProvider.Factory {
        @Suppress("UNCHECKED_CAST")
        override fun <T : ViewModel> create(modelClass: Class<T>): T {
            return TempViewModel(TempUseCase(repository)) as T
        }
    }

    return@lazy ViewModelProvider(this@Activity, factory)[TempViewModel::class.java]
}

Provider Template - class

internal object VieModelFactory {
    inline fun <reified VM : ViewModel> getViewModel(
        owner: ViewModelStoreOwner,
        crossinline creator: () -> VM
    ): VM {
        val factory = object : ViewModelProvider.Factory {
            @Suppress("UNCHECKED_CAST")
            override fun <T : ViewModel> create(modelClass: Class<T>): T {
                return creator() as T
            }
        }
        return ViewModelProvider(owner, factory)[VM::class.java]
    }
}

// use
val viewModel by lazy {
		ViewModelFactory.getViewModel<TempViewModel>(this@Activity) {
				TempViewModel(TempUseCase(TempRepository()))
		}
}

• VM - 제네릭 타입
• inline + reified - 컴파일 시 제네릭 타입 정보가 사라지지 않도록 하여 VM::class.java 같은 런타임 타입 참조가 가능 (Kotlin에서 제네릭 타입은 런타임에 타입 소거**)**
• crossinline - 람다 내부에서 return 을 못 하게 방지

LiveData for event only

class MutableEventData() : EventLiveData() {
    fun notifyEvent() {
        super.setValue(true)
    }
    fun postEvent() {
        super.postValue(true)
    }
}

open class EventLiveData() : LiveData<Boolean>() {}

// use - ViewModel
private val _sendEvent: MutableEventData = MutableEventData()
val sendEvent: EventLiveData get() = _sendEvent

// use - View
viewModel.sendEvent.observe(this) {
	// TODO
}