[TIL] 🌼24/05/01🌼#Sealed Class와 Flow로 Retrofit 응답 처리

[TIL] 🌼24/05/01🌼#Sealed Class와 Flow로 Retrofit 응답 처리

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Sealed Class와 Flow로 Retrofit 응답 처리

• 카카오 이미지/동영상 검색 API를 사용하는 검색 앱에서
  API 응답을 Sealed Class와 Flow로 처리하도록 리팩토링을 진행했다!

📌참고자료

• Using Sealed class in Android for handling API response

sealed class Result<out T : Any> {
    data class Success<out T : Any>(val data: T) : Result<T>()
    data class Error(val exception: Exception) : Result<Nothing>()
    object Loading : Result<Nothing>()
}

fun handleApiResponse(response: ApiResponse) {
    when (response) {
        is ApiResponse.Success -> {
            // handle success
        }
        is ApiResponse.Error -> {
            // handle error
        }
        ApiResponse.Loading -> {
            // handle loading
        }
    }
}

• [Android] Sealed Class 를 Retrofit 통신(with Hilt, flow)

• API 응답 처리에 사용할 Sealed Class 정의하기 (ApiResponse.kt)
  • 제네릭 타입 사용 -> 여러 API 응답 처리 가능

sealed class ApiResponse<out T>{
    object Loading: ApiResponse<Nothing>()
    data class Success<T>(val data: T): ApiResponse<T>()
    sealed class Fail: ApiResponse<Nothing>() {
        data class Error(val code: Int, val message: String?) : Fail()
        data class Exception(val e: Throwable) : Fail()
    }
}

• 카카오 이미지/동영상 검색 API Retrofit 통신 응답으로 받는 DTO 클래스 (KakaoSearchDTO.kt)

data class KakaoSearchDTO<T:Document>(
    val meta: Meta,
    val documents: List<T>?
)

data class Meta(
    @SerializedName("total_count")
    val totalCount: Int,
    @SerializedName("pageable_count")
    val pageableCount: Int,
    @SerializedName("is_end")
    val isEnd: Boolean
)

sealed interface Document {
    data class ImageDocument(
        val collection: String,
        @SerializedName("thumbnail_url")
        val thumbnailUrl: String,
        @SerializedName("image_url")
        val imageUrl: String,
        val width: Int,
        val height: Int,
        @SerializedName("display_sitename")
        val displaySitename: String,
        @SerializedName("doc_url")
        val docUrl: String,
        val datetime: String
    ):Document

    data class VideoDocument(
        val title: String,
        val url: String,
        val datetime: String,
        @SerializedName("play_time")
        val playTime: Int,
        val thumbnail: String,
        val author: String
    ):Document
}

• Repository에서 API 응답(KakaoSearchDTO)을 Sealed Class(ApiResponse)로 변환하여 emit 하기 (ItemRepositoryImpl.kt)

class ItemRepositoryImpl @Inject constructor(
    private val kakaoSearchSource: KakaoSearchApi
) : ItemRepository {
    override suspend fun getImages(query: String): Flow<ApiResponse<KakaoSearchDTO<Document.ImageDocument>>> =
        handleKakaoSearchDTO {
            kakaoSearchSource.getImageDTO(query)
        }

    override suspend fun getVideos(query: String): Flow<ApiResponse<KakaoSearchDTO<Document.VideoDocument>>> =
        handleKakaoSearchDTO {
            kakaoSearchSource.getVideoDTO(query)
        }

    private fun <T:Document> handleKakaoSearchDTO(
        execute: suspend () -> KakaoSearchDTO<T>
    ): Flow<ApiResponse<KakaoSearchDTO<T>>> = flow {
        emit(ApiResponse.Loading)
        try {
            emit(ApiResponse.Success(execute()))
        } catch (e: HttpException) {
            emit(ApiResponse.Fail.Error(e.code(), e.message()))
        } catch (e: Exception) {
            emit(ApiResponse.Fail.Exception(e))
        }
    }
}

• API 응답 결과를 사용하는 ViewModel에서 emit된 값 collect하여 사용하기 (SearchViewModel.kt)
  • 이미지 검색 결과와 동영상 검색 결과 combine으로 합쳐서 사용

	private val _searchItems = MutableStateFlow<List<Item>>(emptyList())
    
    private suspend fun fetchSearchResult() {
        val query = _keyword.value ?: ""

        val imageResponseFlow = itemRepository.getImages(query)
        val videoResponseFlow = itemRepository.getVideos(query)

        imageResponseFlow.combine(videoResponseFlow) {i, v ->
            val itemList = mutableListOf<Item>()
            if(i is ApiResponse.Success){
                itemList.addAll(i.data.documents?.map { it.convert() } ?: emptyList())
            }
            if(v is ApiResponse.Success){
                itemList.addAll(v.data.documents?.map { it.convert() } ?: emptyList())
            }
            itemList.toList()
        }.collect{
            _searchItems.value = it
        }
    }

    private fun Document.ImageDocument.convert() =
        Item(
            itemType = ItemType.IMAGE_TYPE,
            imageUrl = imageUrl,
            source = displaySitename,
            time = datetime.formatDate()
        )

    private fun Document.VideoDocument.convert() =
        Item(
            itemType = ItemType.VIDEO_TYPE,
            imageUrl = thumbnail,
            source = author,
            time = datetime.formatDate()
        )