Concurrency with Kotlin Flow
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In this demo, you’ll see how to use the filter operator you covered in the previous lesson and also how to use the
flatMapLatest operator from the transforming operators’ lesson.
private fun category(categoryId: String): Flow<MovieCategoryViewState> =
movieRepository.categories()
.filter { category -> category.id == categoryId }
.map { category -> MovieCategoryViewState(category.id, category.name) }
import kotlinx.coroutines.flow.*
@OptIn(ExperimentalCoroutinesApi::class)
private fun moviesForCategory(categoryId: String): Flow<List<MovieViewState>> =
movieRepository.categories()
.filter { it.id == categoryId }
.flatMapLatest { movieCategory -> movieRepository.fetchMoviesForCategory(movieCategory.name) }
.map { movies ->
movies.map { movie ->
val imageRes = movieRepository.fetchMovieImage(movieId = movie.id)
MovieViewState(movie.id, movie.title, "", imageRes)
}
}
import kotlinx.coroutines.ExperimentalCoroutinesApi
fun fetchMoviesForCategory(categoryName: String): Flow<List<Movie>> = flow {
val movies = movieService.fetchMoviesForCategory(categoryName)
emit(movies)
}