Concurrency with Kotlin Flow
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This will be another short demo. You’ll see how to handle slow responses in flows using the timeout operator.
@OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class) // HERE
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)
}
}
.timeout(3000.milliseconds) // HERE
.catch { throwable ->
Log.e("CategoryViewModel", "Error happened", throwable)
emit(emptyList())
}
import kotlin.time.Duration.Companion.milliseconds
fun fetchMoviesForCategory(categoryName: String): Flow<List<Movie>> = flow {
delay(5000) // Add a delay of 5 seconds
val movies = movieService.fetchMoviesForCategory(categoryName)
emit(movies)
}