GetPosts.kt

import clean.architecture.example.UseCase
import clean.architecture.example.data.model.Post
import clean.architecture.example.data.source.PostDataRepository
import clean.architecture.example.data.source.PostDataSource

class GetPosts(private val mDataRepository: PostDataRepository) : UseCase<GetPosts.RequestValues, GetPosts.ResponseValue>() {

    protected override fun executeUseCase(requestValues: GetPosts.RequestValues?) {
        mDataRepository.getPosts(requestValues?.userId ?: -1, object : PostDataSource.LoadPostsCallback {
            override fun onPostsLoaded(posts: List<Post>) {
                val responseValue = ResponseValue(posts)
                useCaseCallback?.onSuccess(responseValue)
            }

            override fun onError(t: Throwable) {
                // Never use generic exceptions. Create proper exceptions. Since our usecase is different we will go with generic throwable
                useCaseCallback?.onError(Throwable("Data not found"))
            }
        })
    }

    class RequestValues(val userId: Int) : UseCase.RequestValues

    class ResponseValue(val posts: List<Post>) : UseCase.ResponseValue
}